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ECONOMIC GEOLOGY 



THE UNITED STATES 



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ECONOMIC GEOLOGY 

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UNITED STATES 



WITH BRIEFER MENTION OF FOREIGN MINERAL 
PRODUCTS 



BY 



RALPH S. TARR, B.S., F.G.S.A. 

Assistant Professor of Geology at Cornell University 







Nefo gork 
MACMILLAN AND CO. 

AND LONDON 
1894 

All rights reserved 



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Copyright, 1893, 
By MACMILLAN AND CO. 



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jSTortoootJ ^rfgs : 

J. S. dishing & Co. — Berwick & Smith. 

Boston, Mass., U.S.A. 



PREFACE. 

The object in preparing this treatise is to supply the press- 
ing need of a text-book to accompany a series of lectures given 
by the author to a class in Economic Geology at Cornell Uni- 
versity. At first it was the intention to prepare merely a set of 
lecture notes ; but since this is at best a temporary and unsatis- 
factory expedient, and since the literature is so barren of works 
on this important subject, the author has decided to issue a 
text-book, with the hope that it may find a wider field than that 
for which it is primarily intended. It is a surprising fact that 
there is no text-book on Economic Geology which is sufficiently 
recent to be of value, and that nearly all of the books which have 
been issued on the subject treat exclusively of that part of 
economic geology which is in reality of least importance, and 
give no consideration to the large and important group of non- 
metallic minerals and rocks. 

In the preparation of the book especial attention has been 
given to the mineral products of the United States ; and foreign 
localities are referred to only where they are of marked impor- 
tance, or where they throw some light upon the origin of the 
materials. Even in this country only the most important and 
best known localities are described, types being chosen rather 
than large numbers of variable occurrences ; and, throughout the 
various chapters, the prime object is to point out the geological 
aspect of the subject, and secondarily the economic importance 



VI PREFACE. 

and relation of the several products. The scope of the work 
would need to be considerably enlarged to include much more 
than has been included here, and the expansion of the subject 
beyond this elementary outline must be left to the instructor. 
At times the treatment of the subject is somewhat dogmatic, 
since it is not possible, in such a small space, to always explain 
in detail the arguments upon which conclusions are based ; but 
so far as possible this has been done. There is also some repe- 
tition ; but this is intentional, and is introduced in order to 
illustrate the same principle from different standpoints. 

Whenever possible, the localities chosen for description are 
those with which the author is personally familiar ; but, in a 
field so broad, and covering so many diverse industries, it is 
scarcely possible for one person to possess information concern- 
ing all, or even a large proportion, of the typical occurrences, or 
even of all the industries. The work is, therefore, in many 
parts a compilation, and free use has been made of all available 
sources. This has sometimes amounted to an abstract of descrip- 
tions or conclusions, but rarely to actual quotations, since a more 
condensed statement than is usually found in such sources is 
needed here. The statistics are almost entirely compiled from 
the standard sources, and, where more detailed information is 
desired upon these subjects, reference may be made to these 
original sources. 

Aside from the geological reports of the state and national 
geological surveys, and from special articles in the scientific 
journals, particularly the Engineering and Mining Journal, geo- 
logical descriptions have been obtained from Phillips's Ore 
Deposits and the Census Reports. The purely statistical, and 
a considerable part of the economic portions of the treatise have 
been obtained from the annual reports of the Director of the 



PREFACE. VI 1 

Mint ; the reports upon the Mineral Resources of the United 
States, edited by Dr. D. T. Day under the auspices of the 
United States Geological Survey ; the reports of the Census 
Bureau, particularly the volume on Mineral Industries in the 
reports of the Eleventh Census ; and the Mineral Industry, 
etc., for 1892, edited by Mr. R. P. Eothwell, editor of the 
Engineering and Mining Journal. Particular acknowledgment 
is due the last-named work, since it contains a more valuable 
body of statistics and economic material, written by experts 
upon these subjects, than any other source ; and, moreover, by 
the remarkable energy of its editor, the statistics are brought 
down to the close of 1892, and published a few months after its 
close. One will find there almost every variety of statistical and 
economic information upon the subjects treated. Prom these 
sources the statistics have been compiled, in some cases from 
one, in some from all combined, according as the needs of the 
work were best served. It has not seemed desirable to make 
direct acknowledgments in the following pages, excepting where 
some especial service can be rendered the student by direct ref- 
erence to particularly valuable essays and monographs. 

R. S. TARR. 
Ithaca, N.Y., Sept. 5, 1893. 



CONTENTS. 

Part I. — Introductory Chapters, 
chapter I. 

Common Rock and Vein-forming Minerals ..... 1-27 

Elements and Minerals 1-4 

Common Rock-forming Minerals 5-10 

Quartz o-Q 

Feldspar Group 6-7 

Amphibole Group . 7-8 

Pyroxene Group . . .8 

Mica Group 8-9 

Calcite 9 

Dolomite 10 

Useful Minerals .11-15 

Carbon Group . . . 11-12 

Phosphate of Lime 12-13 

Gypsum 13 

Salt 13 

Corundum .......... 13 

Cobalt Minerals 13-14 

Chromite 14 

Magnesite 14 

Talc '*..... 14-15 

Asbestos .......... 15 

Common Vein-forming Minerals and Ores 15-27 

Character of Ores 15-17 

Common Veinstones 17 

Fluorite 17 

Barite 17 

Common Ores 17-27 

Iron 18-20 

Gold ' .20 

ix 



CONTENTS. 



Platinum 

Silver 

Copper 

Lead 

Zinc 

Mercury 

Manganese 

Aluminum 

Tin . 

Nickel 

Antimony 



PAGES 

21 

21-22 

22 

22-23 

23-24 

24 

24-25 

25 

25 

26 

26 



CHAPTER II. 

Rocks or the Earth's Crust 28-51 

Sedimentary Rocks . . . 28-34 

Chemically precipitated Rocks 30-31 

Organic Rocks 31-32 

Conditions of Accumulation 32-34 

Igneous Rocks 34-38 

Metamorphic Rocks . . . 38-41 

Geological Age of Rocks 41-48 

Age of Metamorphic Rocks ....... 41-42 

Age of Eruptive Rocks 42-43 

Age of Sedimentary Rocks ' . 43-48 

Disturbance of the Rocks 48-51 



CHAPTER III. 

Physical Geography and Geology of the United States 
Coastal Plains . 

Quaternary Coastal Plains 

Florida Plains 

Tertiary Coastal Plains . 

Cretaceous Coastal Plains 

Triassic Coastal Area . 
Mountains of the Eastern States 

The Eastern Archean Mountains 

Appalachian Mountain Region 
Central Plains .... 



52-71 

52-58 

52-54 

54 

54-55 

55-56 

56-58 

58-61 

58-59 

59-61 

61-62 



CONTENTS. 



XI 



Lake Superior Region 63 

Cordilleran Region 63-65 

Summarized Geological History . . . • . . . 65-71 



CHAPTER IV 

Origin of Ore Deposits 
Original Condition . 
Removal of Original Ores . 
Origin of Cavities 
Joint Planes 
Fault Planes 
Solution Cavities 
Minor Cavities . 
Classification of Ore Deposits . 
I. Eruptive Deposits 
II. Mechanical Deposits . 
III. Chemical Deposits 

(a) Precipitated Deposits 
(6) True Veins . 

i. Chamber Deposits 
ii. Gash Veins 
iii. Fissure Veins 
iv. Ore Channels . 

(c) Replacement Deposits 

(d) Impregnation Deposits 

(e) Concretionary Deposits 
(/) Segregated Deposits 
(g) Contact Deposits . 

Distribution of Ore Deposits 



72-95 

72-73 

74-75 

75-78 

75-76 

77 

77-78 

78 

78-94 

80-81 

81-82 

82-94 

82-83 

83-87 

84 

84 

84-86 

86-87 

87-88 

88-89 

89-90 

90-92 

92-94 

94-95 



CHAPTER V. 

Mining Terms and Methods 96-115 

Mining Terms 96-101 

Variation in Veins 101-103 

Mining Methods 103-109 

Concentration of Ores 110-113 

Reduction of Ores ......... 113-115 



Xll CONTENTS. 

Part II. — Metalliferous Deposits, 
chapter VI. 

PAGES 

Iron 119-146 

General Statement . . . 119-120 

Brown Hematite Ores 120-122 

Red Hematite Ores 122-127 

Magnetite Ores 127-132 

Carbonate of Iron Ores 132-133 

Foreign Occurrences . . . . 133-135 

General Mode of Occurrence 135-136 

Uses of Iron 136-137 

Distribution of Iron Ores in the United States .... 137-144 

Production of Iron 144-146 

CHAPTER VII. 

Gold and Platinum ......... 147-179 

Gold 147-175 

General Statement 147 

Appalachian Gold Fields 147-148 

California Quartz Mines 148-153 

California Auriferous Gravels 153-158 

Origin of Nuggets . 157-158 

Other Western Gold Fields 158-160 

Alaskan Gold Mines 160-161 

Foreign Gold Regions 161-168 

Australasia • .... . 161-163 

Russia and Siberia . . . . . . . . 163-164 

South African Fields 164-165 

Other European and Asiatic Countries . . . 165-166 

South American Countries 166-167 

Mexico and Canada ■ 167-168 

Origin of Gold Deposits 168-170 

Uses of Gold 170-172 

Production of Gold ....... 173-175 

Platinum Group ■ 176-179 

Occurrence of Platinum 176-177 

Uses of Platinum 177-178 

Production of Platinum ....... 178 

Other Metals of Platinum Group . . . . . 179 



CONTENTS. Xlll 



CHAPTER VIII. 

PAGES 

Silver 180-207 

General Statement 180-181 

Silver Mines in the United States 181-193 

Comstock Lode 181-187 

Eureka District 187-189 

Other Silver Mines of the United States .... 189-193 

Mexico, Central America, and Canada 193-195 

South American Silver Mines 195-197 

Australasia 197 

European Silver Mines 197-199 

Origin of Silver 199-201 

Uses of Silver 201-204 

Production of Silver . . 204-207 

CHAPTER IX. 

Copper . . . . 208-227 

General Statement , . . 208-209 

Appalachian States 209-210 

Lake Superior District 210-213 

Montana Mines 214-215 

Arizona and Other Western Mines . . . . . . 215-216 

Foreign Copper Occurrences 216-220 

Occurrence and Origin of Copper 220-222 

Uses of Copper 222-224 

Production of Copper . . . . . . . . 224-227 

CHAPTER X. 

Lead and Zinc 228-252 

Lead 228-243 

General Statement 228 

Appalachian District 229 

Missouri Lead District 229-233 

Colorado Lead Mines 233-235 

Other Western Lead Mines . . . . . . 235-236 

Foreign Lead Occurrences 236-238 

Origin of Lead Ores 238 

Uses of Lead ........ 238-239 

Production of Lead .'..,..■.••. 239-243 



XIV 



CONTENTS. 



Zinc 243-252 

General Statement 243-244 

Zinc in the United States . . 244-245 

Foreign Zinc Mines 245-247 

Origin of Zinc Deposits 247-248 

Uses of Zinc . ■ . ... . . . 248-249 

Production of Zinc 249-252 



CHAPTER XI 

Mercury and Manganese 
Mercury .... 

California Mines 

Foreign Mercury Mines 

Origin of Mercury 

Uses of Mercury 

Production of Mercury 
Manganese 

General Statement 

Manganese in the United States 
. Foreign Manganese Mines 

Origin of Manganese 

Uses of Manganese . 

Production of Manganese . 



253-273 

253-262 

253-255 

255-258 

258-260 

260 

261-262 

262-273 

262-264 

264-266 

266-268 

268-270 

270-271 

271-273 



CHAPTER XII. 

Tin and Aluminum . . . . . . . . . . . 274-291 

Tin 274-283 

General Statement ........ 274-275 

Tin Mines of the United States 275-277 

Foreign Tin Mines . . . . . . . 277-281 

Origin of Tin Ore 281-282 

Uses of Tin . . 282-283 

Production of Tin 283 

Aluminum . . . . . . . . . . 283-291 

Occurrence of Aluminum ....... 283-286 

History and Metallurgy of Aluminum .... 286-287 

Uses of Aluminum 288-290 

Production of Aluminum . . . . , . . 290-291 



CONTENTS. XV 

CHAPTER XIII. 

PAGES 

Miscellaneous Ores and General Review of Metals . . 292-307 

Nickel and Cobalt 292-296 

Mines in the United States 292-293 

Foreign Mines 293-294 

Origin of Nickel and Cobalt 294 

Uses of Nickel and Cobalt 294-295 

Production of Nickel and Cobalt 295-296 

Antimony 297-299 

Chromium 299-300 

Iron Pijrite 300-301 

General Review of Metals 302-307 

Part III. — Non-Metallic Mineral Products. 

CHAPTER XIV. 

Coal 311-336 

General Statement 311-314 

New England Coal Basin . . . . . . . 314-315 

Appalachian Coal District 315-318 

Central, Western, and Northern Coal Areas .... 318-319 

Rocky Mountain, Pacific Coast, and Alaskan Coal Areas . 319-321 

Origin of Coal 321-326 

Conditions Existing in Carboniferous Times .... 326-331 

Uses of Coal , 331-333 

Production of Coal 333-336 

CHAPTER XV. 

Petroleum, Natural Gas, and Asphaltum .... 337-358 

Petroleum 337-349 

General Statement . 337-338 

Distribution of Petroleum . . . . . . 338-340 

Origin of Petroleum 340-346 

Uses of Petroleum 346-347 

Production of Petroleum ....... 347-349 

Natural Gas .... 349-355 

General Statement . . . ' . . . . . 349-352 

Uses of Natural Gas 353-354 

Production of Natural Gas . . . ... . 354-355 

Asphaltum 355-357 

Ozokerite . 357-358 



XVI CONTENTS. 



CHAPTER XVI. 

Building-Stones and Cements ....... 359-390 

Building- Stones 359-386 

General Statement 359-360 

Granite 360-368 

Sandstone 369-372 

Bluestone 372-373 

Slate 373-376 

Limestone 376-380 

Marble 380-383 

Summary of Building-Stone Production .... 383-386 

Natural and Artificial Cements 387-390 

CHAPTER XVII. 

Soils, Clays, Fertilizers, Artesian Wells, and Mineral 

Waters 391-420 

Soils . . . 391-399 

Clays 399-402 

Fertilizers .......... 402-412 

General Statement 402 

Limestone and Marl . . 402-403 

Gypsum 403-405 

Phosphatic Fertilizers 405-412 

Mineral Phosphates 405-406 

Guano 406-407 

Rock Phosphates 407-412 

Artesian Wells 412-418 

Mineral Waters 418-420 

CHAPTER XVIII. 

Precious Stones, Abrasive Materials, Salt, Miscellaneous 
Minerals, and General Summary of Mineral Pro- 
duction . 421-456 

Precious Stones 421-425 

Abrasive Materials 425-429 

General Statement ........ 425-426 

Infusorial Earth . . . . . . . 426 

Corundum and Emery ....... 427 



CONTENTS. XV11 

PAGES 

Grindstones and Buhrstones 427-428 

Oilstones and Whetstones 428-429 

Statistics 429 

Salt 430-434 

Bromine 434 

Borax 434-436 

Natural Soda 437 

Magnesite 437-438 

Sulphur 438-440 

Fluorite 440 

Graphite 441 

Lithographic Stone 442 

Mica ' . 442-445 

Tale and Soapstone 445-447 

Asbestos 447-448 

Barite 448-449 

Mineral Paints 449-450 

General Summary of Mineral Production .... 450-456 

APPENDIX. 

Literature of Economic Geology 457-465 

Text-Books of Mineralogy and Geology 459 

General Treatises upon Economic Geology .... 459-460 

Special Articles 460 

Works upon Special Subjects 460-464 

Iron ..... 460-461 

Gold, Silver, and Lead 461 

Zinc, Copper, Mercury, Manganese, Tin, and Aluminum . 461-462 

Coal 462 

Petroleum .463 

Building- Stones, etc . . . 463 

Soils, Clays, Fertilizers, etc 463-464 

Miscellaneous Minerals 464 

Mineral Statistics . 464 

Mining Methods 464-465 

Alloys and Metallurgy . . 465 

List op Authors and Works of Reference referred to in 

the Text 467 

Index ...'.....«„,. 471 



LIST OF ILLUSTRATIONS. 

Plate Page 

I. Hydraulic Mining • . Frontispiece 

II. Rockport Granite Quarry . • 363 

FlGTJKE 

1. Unconformity 46 

2. Normal and Reverse Fault 50 

3. Anticlines and Synclines 51 

4. Formation of Cavities by Faulting 76 

4a. Formation of Cavities by Faulting 77 

5. Bedded Ore Deposit 83 

6. Fissure Vein 84 

7. Replacement Ore Deposits 87 

8. Impregnation Ore Deposits 88 

9. Concretionary Ore Deposits 89 

10. Segregation Veins 90 

11. Contact Ore Deposits 93 

12. Section of Mineral Vein 98 

13. Section of Mineral Vein showing Horses 99 

14. Section showing Shafts, Tunnels, etc 106 

15. Section showing Mode of Occurrence of Iron in the Penokee 

Region 125 

16. Cross- section of Table Mountain, California 154 

17. Section showing Position of Gold-bearing Gravels in New South 

Wales . ... 163 

18. Cross-section of Comstock Lode, Nevada 185 

xix 



XX LIST OF ILLUSTRATIONS. 

Figure Page 

19. Cross-section of Eureka Vein, Nevada 188 

20. Ideal Section showing Mode of Occurrence of Lead in Wisconsin . 229 

21. "Openings " and Ore Deposits in Galena Limestone, Wisconsin . 230 

22. " Flats," etc., in Galena Limestone, Wisconsin .... 231 

23. Gash Veins and Cave Openings, Galena Limestone, Wisconsin . 232 

24. Cross-section of Lode at Leadville, Colorado 234 

25. Mode of Occurrence of Manganese in Arkansas .... 265 

26. Artesian Wells . 415 

27. Artesian Wells . . .416 






Part I. 
INTRODUCTORY CHAPTERS. 



ECONOMIC OEOLOQY 



OF THE 

UNITED STATES. 

CHAPTER I. 

COMMON ROCK AND VEIN-FORMING MINERALS. 

Elements and Minerals. — Chemical investigations have 
shown that about -f^ of the earth's crust is composed of 
the following sixteen elements : oxygen, silicon, aluminum, 
calcium, carbon, magnesium, potassium, sodium, iron, sul- 
phur, hydrogen, chlorine, phosphorus, fluorine, manganese, 
and barium. About ninety-seven per cent of the earth's crust 
is composed of the first nine of these elements. Besides 
these there are over fifty other elements of greater or less 
rarity. Of the elements, oxygen is by far the most important. 
Nearly every element is found united with it, and in these 
various compounds it forms about one-half, by weight, of all 
the rocks. Silicon, next in abundance, is always found united 
with oxygen. 

Some of the elements occur in the earth's crust free from 
union with other elements. Graphite and diamond are pure 
carbon, and gold, silver, copper, and even iron, are also found 

l 



A ECONOMIC GEOLOGY OE THE UNITED STATES. 

free or native. These native elements are, however, extremely 
rare when compared with the great mass of minerals. The 
crust of the earth is oxidized, and whatever may have been 
its original condition or what may be the condition of the 
interior, upon the surface nearly all of the elements are in 
chemical combinations of greater or less definiteness, and 
these are called minerals. 

Minerals occur in the crust in several conditions. Typi- 
cally they are crystalline, or with definite molecular structure, 
as in the igneous and metamorphic rocks and most mineral 
veins. Their structure may be glassy when formed by the 
rapid cooling of a lava, or amorphous (without form), as in 
flint, when precipitated, without crystallization, from solu- 
tion. Any of these minerals, partly by decay, partly by 
mechanical destruction, may be removed from the parent 
rock and deposited as sedimentary or stratified rocks. The 
minerals are then fragmented, as in sandstones or shales. 
Some minerals are dissolved from the rock and later pre- 
cipitated, as in the case of gypsum, or formed into a sedi- 
mentary rock by the intervention of calcareous secreting 
animals. In such cases the minerals are usually amorphous. 

Theoretically, minerals have not only a definite chemical 
composition, but also a definite geometric form. The com- 
ponent molecules build themselves together according to 
definite laws ; and when their growth is not interfered with, 
crystals are formed according to these laws, and the resulting 
crystal form is capable of mathematical calculation. Con- 
ditions which permit this perfect development are compara- 
tively rare in nature, and consequently perfectly formed 
crystals are not common ; but in most cases the tendency 
is shown by definite molecular structure with well-defined 



COMMON ROCK AND VEIN-FORMING MINERALS. 3 

optical characters. In mineralogy the ciystallographic study 
is of prime importance, 1 but in an economic study of minerals 
it is less important than the chemical composition and the 
ever-present physical characters. 

A few predominant chemical compounds make up the 
greater part of the earth's crust. Of these, silica (Si0 2 ), a 
combination of silicon and oxygen, is the most important. 
This forms quartz and its numerous varieties, amethyst, 
agate, flint, etc. ; and, combined with other elements, often 
with an extremely complicated chemical composition, silica 
makes the great group of silicates, which includes the larger 
number of the common rock-forming minerals. Oxygen com- 
bined singly with an element forms another great group, the 
oxides to which many ores, such as those of iron, belong. 
Combined with aluminum oxygen forms alumina (A1 2 3 ), 
a common mineral; and this combined with silica is the 
base of our clays and an important rock constituent. Oxygen 
with carbon and some other element forms the carbonates to 
which limestones belong; with sulphur and some other ele- 
ment it forms the sulphates (gypsum, etc.) ; and with phos- 
phorus and another element the phosphates. Sulphur, 
without oxygen, combined with an element forms a sulphide, 
fluorine a fluoride, chlorine a chloride, etc. 

The elements are divided into two groups, the metals and 
the metalloids. This division was made at a time when the 
known elements were fewer than at present, and was based 
upon the possession or absence of metallic characters ; but it is 
now known that this division of elements is not as sharp as was 
at first supposed, though for the types of the two groups it still 

1 In Dana's works on mineralogy the subject of crystallography is treated, 
but the best work upon the subject is Williams' Elements of Crystallography . 



4 ECONOMIC GEOLOGY OF THE UNITED STATES. 

holds. Of the sixteen elements above mentioned, oxygen, 
silicon, carbon, sulphur, hydrogen, chlorine, phosphorus, and 
fluorine are metalloids ; the remaining eight are metals. 
Many of the metals are of economic value, because of certain 
properties which they possess ; but the metalloids, excepting 
carbon and sulphur, are of little importance in the free state. 
Nearly all common minerals, excepting quartz, contain 
metals in their composition, but the great majority have the 
metals either in such small quantities or in such refractory 
combinations that they are not separated. From the eco- 
nomic standpoint minerals are of importance in three distinct 
conditions. As rock-forming minerals, making a structure 
which can be utilized in the arts, some of the more common 
silicates are important. Secondly, certain minerals are of 
importance as minerals; the phosphates for fertilizers, the 
hydrocarbons for fuels and light, gypsum for plaster, and 
certain minerals which, because of rarity or beauty, are used 
as gems. Thirdly, many minerals are of value for the metal 
which they hold in chemical combination, and which man 
finds it profitable to extract. These three groups will be 
considered separately. In the first group are included quartz, 
feldspar, hornblende, augite, mica, calcite, and dolomite ; in 
the second, carbon, sulphur, phosphate of lime, gypsum, salt, 
corundum, cobalt minerals, chromite, magnesite, talc, soap- 
stone, and asbestos ; in the third group, the ores and veinstones. 1 

1 This consideration of minerals is general, and should be supplemented 
by a study of the minerals themselves, preferably by a thorough course in 
mineralogy. The object in treating the minerals here is to give promi- 
nence to an aspect of the subject not usually found in text-books of 
mineralogy. The relations and characters of the rock-forming minerals 
are found in Rosenbusch's Microscopical Physiography, Vol. I. Translated 
by Iddings. 



COMMON ROCK AND VEIN-FORMING MINERALS. 5 

Common Rock-forming Minerals. — Quartz (Si0 2 ) occurs in 
many forms in the earth, being very variable in colour, but 
commonly either glassy, or clouded whitish or black, though 
frequently coloured, as in amethyst. It has a glassy lustre, 
is hard, scratching glass readily, and is not scratched by the 
knife. There is no cleavage, but the mineral breaks with a 
rounded conchoidal fracture like glass. The specific gravity 
is low. Being both hard and not easily destroyed chemically, 
it is a very durable mineral, and remains long after many of 
the associated minerals have been decayed. Ordinary acids 
do not attack it, but it is soluble in small quantities in water, 
particularly when the water is charged with organic acids or 
alkaline carbonates. Hence quartz is transported by the 
water which creeps through the earth and is deposited in 
veins, and as a cement to many siliceous rocks, sometimes 
transforming sandstones to compact quartz or quartzite. 
That it is present both in fresh and salt water is shown by 
the fact that certain plants (Diatoms) and animals (Infusoria) 
build their shells or tests of silica which they extract from 
the water. There is no mineral more common than quartz. 
Sandstones are made up almost entirely of quartz grains, the 
fragmental remnants of previously existing rocks which have 
disintegrated and given up their less durable minerals to 
form clay. Gneiss and schist, rocks derived by metamorphism 
from other rocks, are in part made up of quartz, which, in 
some cases, forms the bulk of the rock. The original con- 
dition of quartz, as in the case of a great majority of minerals, 
is in eruptive rocks. Certain of these rocks, notably the 
granites, rhyolites, and quartz porphyries, contain this min- 
eral as an essential constituent, it being one of the two 
predominant minerals. Aside from these common occur- 



6 ECONOMIC GEOLOGY OF THE UNITED STATES. 

rences quartz is found in less abundance in many other rocks, 
sometimes in large pieces, sometimes in minute and even 
microscopic grains. 

Feldspar Group. — The group of feldspars is divided into 
many species, but it is necessary to recognize here only the 
two main subdivisions, — the orthoclase, or potassium group 
(K 2 OAl 2 3 Si0 2 ), and the plagio.clase, or lime soda group 
(Na 2 OCaOAl 2 3 Si0 2 ). Aside from the chemical basis for 
this division there is also a crystallographic difference, each 
group belonging to a different system. Both groups have 
certain characteristics in common. There are well-defined 
cleavages, 1 the specific gravity is low, and the hardness less 
than in quartz, but just beyond the touch of the ordinary 
knife. The colour is usually dull and whitish, from decay, 
though green and reddish colours are not uncommon, and 
some fresh feldspars are colourless and glassy. On the cleav- 
age faces the lustre is pearly, but on the rough fracture it is 
glassy. They differ somewhat in their ability to decay, but 
all are destructible ; and the different species, being of dif- 
ferent chemical composition, decay at different rates. The 
chief difference, and the only one that can be made use of in 
the absence of a microscope, or a chemical analysis, provided 
the crystal form is not present, is the presence or absence of 
fine striations on one of the cleavage faces. These are very 
noticeable on some plagioclases, but never on orthoclase ; but, 
as it is not universally present, it is not of much value, and 
hence in this statement but little stress can be placed upon 
the division of the feldspars. An acquaintance with the 
rocks usually serves to indicate this difference in the feld- 

1 A cleavage is a smooth fracture plane in a definite direction with refer- 
ence to the crystal faces or the crystallographic axes. 



COMMON ROCK AND VEIN-FORMING MINERALS. 7 

spars, but this can only come after long experience in 
examining them. Feldspar, even in small grains, can usually 
be told from quartz by the presence of the smooth cleavage 
faces, and usually by the clouded, somewhat decayed appear- 
ance, contrasted with the fresh glassy appearance of the 
quartz. 

The feldspars are extremely abundant and their distribu- 
tion very widespread. In the igneous rocks they are more 
abundant than quartz, since in one form or another they 
appear in nearly all the common varieties. The feldspars 
are almost equally abundant in the metamorphic gneisses 
and schists. When attacked by weathering and percolating 
water, being chemically complex, they begin to decay and 
form simpler compounds. The salts of potassium, sodium, 
and calcium are transformed chiefly to soluble minerals 
which are carried away in solution, while the silica and 
alumina form quartz and kaolin, a hydrous silicate of alumina 
(H 2 Al 2 Si 2 8 + H 2 0), which is the chief constituent of many 
clays. 

Amphibole Group. — To this group belong hornblende, 
which is the most common, tremolite, actinolite, etc. Horn- 
blende is a silicate of magnesia with lime, iron, usually 
alumina, and a small percentage of other compounds. The 
colour varies in the amphiboles from black to white, but 
common hornblende is usually either black or dark green, 
the intensity of the colour varying with the per cent of iron 
and other metallic compounds. It is hard, heavier than 
either quartz or feldspar, has a glassy lustre, a conchoidal 
fracture, and a fairly perfect cleavage in two directions, with 
a pearly lustre on these faces. In granites, diorites, gneisses, 
and schists, it is common, and in many other rocks it occurs 



8 ECONOMIC GEOLOGY OF THE UNITED STATES. 

in less abundance. Owing to the readiness with which it 
decays, it is rarely found in the sedimentary rocks, although 
the products of its destruction enter frequently into the 
clays and shales. 

Pyroxene Group . — The only common mineral of this 
group is augite, which resembles hornblende very closely 
both in chemical composition and physical structure. In- 
deed, unless the crystal form or the cleavage can be seen, 
the two cannot be told apart in the rocks. Generally the 
augite is more greenish in colour than hornblende, but 
unless the two are seen side by side, this hardly serves to 
distinguish them. The cleavage of augite is nearly rec- 
tangular, while that of hornblende forms a much greater 
angle. Augite is much less abundant than hornblende, but 
in some of the lavas, such as basalt and diabase, as well 
as in some of the gneisses, it is the predominating mineral. 

Mica Group. — Mica is a family name applied to a wide 
variety of species which, however, can be considered here 
under two general groups, the white or muscovite mica and 
the black or biotite mica. Both are silicates of alumina with 
iron, potassium, magnesium, sodium, and other elements in 
smaller quantities. The white mica contains little iron, 
while the black mica sometimes carries as much as twenty- 
eight per cent, the intensity of the blackness being usually 
proportional to the amount of iron. The true muscovite is 
very nearly transparent, while the extremely black biotite 
barely allows light to pass through thin flakes. In specific 
gravity they are about as heavy as hornblende, but there is 
some difference among them, the very ferruginous micas being 
a little heavier than the muscovite. They resemble each other 
in hardness (being easily scratched with the knife), in their 



COMMON ROCK AND VELN-FORMING MINERALS. 9 

pearly lustre, but primarily in their remarkable cleavage, 
which allows them to be split readily into extremely thin, 
elastic plates. When occurring in fine grains, as in granites, 
it is sometimes difficult to distinguish the black mica from 
hornblende ; but the remarkable cleavage is easily recognized, 
and this serves as a distinguishing feature. 

In the rocks mica is perhaps most abundant in the schists 
and gneisses, though it is present also in many granites as 
an essential constituent, and also in other igneous rocks as 
an essential or accessory mineral. The white mica does not 
decay readily, and is consequently present in many sand- 
stones. Biotite is also present in some of the sedimentary 
rocks, but it usually decays by the loss of iron and some of 
the soluble salts, and the absorption of water. Chlorite is 
then formed, and this mineral is found in clays and other 
sedimentary rocks often in great abundance. It is present in 
some schists, giving to them, as also to the clays, a greenish 
colour. It can be distinguished from anhydrous mica by its 
green colour and the marked cleavage, forming flakes which 
are no longer elastic. 

Calcite (CaC0 3 ) is commonly either colourless or white, 
as in white marbles, though various colours are sometimes 
assumed. It is soft, of low specific gravity, and can be told 
from other common minerals by its action upon the appli- 
cation of dilute hydrochloric acid, when a brisk effervescence 
is caused. In the rocks it occurs, as a very widespread 
constituent, in minute quantities, in many igneous, meta- 
morphic, and sedimentary rocks, but as the main constituent 
of limestone and its metamorphosed product, marble. In 
these strata it is usually impure by an admixture of clay or 
some foreign minerals which give various colours to the rock. 



10 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Dolomite. — Not uncommonly the carbonate of lime is 
combined chemically with magnesium, and the resulting 
mineral is dolomite ([Ca, Mg]C0 3 ). This resembles calcite 
very closely, but does not effervesce with weak, cold acids, 
though it will effervesce when the acid is heated. There are 
many dolomitic limestones, but in other rocks the mineral 
is uncommon. Both dolomite and limestone are used not 
only for building-stones, but also for a source of lime, and as 
a fertilizer. 

The above minerals constitute the greater part of the 
rocks of the earth's crust. The only other really abundant 
minerals are the ores of iron which are scattered through 
all rocks as well as gathered together into veins. Sand- 
stone is practically all quartz, or quartz and kaolin ; lime- 
stone and marble are either dolomite or calcite, and shales 
and clays are practically all composed of the decayed 
products, or finely ground fragments of some of the above 
minerals. Granite and the metamorphic gneisses and schists 
are composed chiefly of quartz and feldspar with either horn- 
blende, mica, or augite, or a combination of these. The 
other igneous rocks are chiefly composed of feldspar, with 
hornblende, mica, or augite, or a combination of two or all 
three of these minerals. They are the essential minerals 
of the earth's crust, and other minerals are accessories, 
although in some rocks a rarer mineral may be in such 
quantities as to be an essential constituent of these partic- 
ular rocks. For instance, a basalt may have enough olivine 
to become an olivine basalt, or a schist may be a tourmaline, 
epidote, or talc schist when one of these minerals is abun- 
dant ; but for our purposes the rarer kinds of rock-forming 
minerals may be neglected. 



COMMON ROCK AND VEIN-FORMING MINERALS. 11 

Useful Minerals. — This group, which includes those indi- 
vidual minerals used without chemical change, is a very 
large one, but only a few will be described. There are 
many rare minerals, such as the gems belonging to this 
class, but it is hardly necessary to describe these here. 

Carbon Group. — The minerals belonging to this group 
are of three distinct kinds, — (1) the organic material of indefi- 
nite composition stored in the earth and in places trans- 
formed to coal or mineral oils, (2) graphite, and (3) dia- 
mond. Coal is not properly a mineral ; at least, it is not 
strictly the element carbon, but rather a hydrocarbon con- 
sisting of a great variety of chemical and mechanical mix- 
tures. Yet from the stage of pure wood there is every 
gradation to graphite, through peat, lignite, bituminous coal, 
anthracite, and graphitic anthracite. Allied to this group is 
asphaltum, which in turn grades to mineral oils, and these 
to various indefinite carbonaceous compounds stored in the 
rocks. Carbon in these forms exists not only in beds and 
other accumulations, but also disseminated through many of 
the stratified rocks, particularly shales and limestones, where 
the black colour is often due to these hydrocarbons derived 
from the remains of animals or plants fossilized in the rock. 
With the hydrocarbon there is frequently some pure carbon. 

When rocks are altered by heat, or by folding with accom- 
panying heat, these carbonaceous substances are slowly 
transformed, in many cases, to fixed carbon, or graphite. 
Thus in metamorphic rocks, which are the result of the 
alteration of sedimentary strata, graphite is common in 
flakes and often in veins. Among marbles this is a common 
phenomenon. Aside from these occurrences graphite is found 
both in flakes and in veins in rocks which are not so cer- 



12 ECONOMIC GEOLOGY OF THE UNITED STATES. 

tainly of sedimentary origin, and here its occurrence is not 
so easily explained. Graphite is a dead black mineral with 
a dull metallic lustre, a greasy "feel," and a hardness so low 
that it soils the fingers. 

Diamond, the other form of fixed carbon, is, when pure, 
perfectly colourless, with an extremely brilliant lustre and a 
hardness greater than that of any other mineral. Its origin 
is not definitely known, but it seems probable that it is the 
result of a very slow metamorphism of some previous con- 
dition of disseminated hydrocarbon. 

Sulphur is found in the earth not only "in combination 
with other elements, but also native, sometimes the result 
of solfataric action near volcanoes, but frequently the 
product of disintegration of some sulphate or sulphide. It 
is usually yellow, soft, brittle, of low specific gravity, and 
with a resinous lustre. 

Phosphate of lime is usually the result of animal accumu- 
lations. The bone beds and guano deposits are directly of 
this origin, but are impure both by chemical and mechani- 
cal combinations. Phosphatic matter is found not only in 
considerable accumulations, but also disseminated through 
the sedimentary rocks, so that when these are metamor- 
phosed, the mineral phosphate, apatite (Ca 3 P 2 8 with some 
chlorine or fluorine), is produced. Not only is it found in 
places where its origin seems organic, but also as an acces- 
sory mineral, in scattered crystals in many truly igneous 
rocks as well as in massive gneisses. In the latter it is 
sometimes found also in veins. Apatite is of medium spe- 
cific gravity, it can be scratched with a knife, its colour is 
variable, though most commonly greenish, and its lustre is 
vitreous. Only when found in veins is it of economic 



COMMON ROCK AND VEIN-FORMING MINERALS. 13 

importance, though its presence in the rocks adds to the 
value of the soil resulting from their disintegration. 

G-ypsum, the sulphate of lime (CaS0 4 + water) is easily 
scratched with the knife, has a marked cleavage with a 
pearly lustre, and is usually white in colour. It is present 
in solution in most water, giving to it the property known 
as " hardness." In the ocean gypsum exists in solution, and 
consequently sedimentary rocks of marine origin have this 
mineral disseminated through them. By the evaporation 
of salt lakes gypsum becomes concentrated as does salt, and 
it is frequently precipitated in beds when these bodies of 
water are destroyed by desiccation. Limestone beds are 
at times transformed to gypsum by the accession of sulphur 
carried in solution from some source, frequently the decay 
of sulphides or sulphates ; and, by a similar process, gypsum 
is sometimes formed about sulphur springs and volcanoes. 

Salt is present in many rocks, particularly those of sedi- 
mentary origin, and it is derived from the decay of rocks by 
the union of chlorine and sodium. As a mineral it is usu- 
ally formed in the earth by precipitation from a dead sea, 
though much of the salt supply comes from a brine which is 
present in sandstones of certain ages. 

Corundum (A1 2 3 ), when pure, bears a marked resem- 
blance to quartz, but it can be distinguished from this by 
its cleavage and excessive hardness, being next, in the scale 
of hardness, to diamond. The two pure forms of this min- 
eral, corundum and sapphire, are comparatively rare ; but 
emery, a black variety coloured by iron impurities, is more 
common, occurring in veins in metamorphic rocks. 

Cobalt Minerals. — The two most important ores of cobalt 
are smaltite and cobaltite. Smaltite is a combination of 



14 ECONOMIC GEOLOGY OF THE UNITED STATES. 

arsenic with cobalt, iron, and nickel in varying quantities. 
It is tin-white or steel-gray, sometimes iridescent from 
tarnish, and has a metallic lustre. It is not easily scratched 
with a knife, and has a high specific gravity. Cobaltite 
(CoAsS) is silver-white in colour, with a red tinge and a 
metallic lustre. When, as is sometimes the case, a part of 
the cobalt is replaced by iron, its colour is grayish black. 
There is sometimes present on the cobalt ores a peculiar 
apple-green rust, annabergite. These minerals are the source 
of the cobalt compounds in the arts. 

Chromite, or chrome iron ore (FeCr 2 4 ), is the source of 
chromium oxide and the compounds of chromium in use in 
the arts. Its colour is between iron-black and brown-black, 
with a submetallic lustre. It can be scratched with the 
knife with difficulty, and is of moderately high specific 
gravity. The verd antique marble owes its colour partly 
to this ore. 

Magnesite. — This comparatively rare mineral is found in 
considerable abundance in California. It is closely allied to 
dolomite, the latter being CaMg(C0 3 ), whereas magnesite 
is simply carbonate of magnesium (MgC0 3 ) without lime. 
It is a brittle mineral of moderate hardness, being scratched 
with the knife, and in colour varies from white to brown, and 
from transparent to translucent. 

Talc (H 2 Mg 3 Si 4 12 ) is a soft mineral with a soapy feeling 
and a greasy lustre, and a colour varying usually from 
green to grayish white. The lustre is pearly on the cleavage 
faces, and the cleavage is well developed, so that the mineral 
splits easily into thin laminae, but these are not elastic as 
in micas. Soapstone is a variety of this, usually more or less 
impure. These minerals occur very commonly in meta- 



COMMON ROCK AND VEIN-FORMING MINERALS. 15 

morphic rocks, particularly in the less gneissic schists, where 
talcose slates and schists are abundant. 

Asbestos. — Two very different minerals are included under 
this name in commerce, owing to their common fibrous 
nature. One, the true mineralogical asbestos, is one of the 
amphiboles and is allied to actinolite, of which it is one 
variety. Chemically, it is a silicate of lime, magnesia, and 
iron (Ca[MgFe] 3 Si 4 12 ). It crystallizes in fibres which 
are capable of being woven into a fire-proof cloth, the ami- 
anthus of the Greeks. The second form of asbestos is 
chrysotile, a fibrous variety of serpentine (H 4 Mg 3 Si 2 9 ). It 
has a silky lustre, and usually a greenish white colour, and 
has nearly the same properties as true asbestos. 

To these might be added calcite and dolomite (described 
above), since they are used in the manufacture of lime and 
for a fertilizer, serpentine, and the various gems, as well as 
the veinstones, fluorite and barite. 1 

Common Vein-Forming Minerals and Ores. — Character of 
Ores. The ores, though of so much importance from the stand- 
point of economic geology, are, with the exception of those of 
iron, comparatively rare. An ore may be defined as a mineral 
with a metallic base. It may be a native metal, or it may 
consist of two parts, a metal and a mineralizer, which may be 
a single element (usually a metalloid) or several elements. 
Properly speaking, the metallic constituent should be a pre- 
dominant constituent. For instance, biotite, which contains 
iron, is not an ore, because the metal is in such small quantities. 
The miner considers an ore to be a mineral with a metallic 
base, occurring in sufficient abundance to be economically 
valuable ■ but, from the scientific standpoint, a grain of 

i See p. 17. 



16 ECONOMIC GEOLOGY OF THE UNITED STATES. 

magnetite in a granite rock is as much an ore as a bed of 
this mineral. 

According to the mineralizer, or the chemical composition 
of an ore, we have a basis for the classification of ores, and, 
indeed, of all minerals. Some elements occur native; that is, 
free from combination with metalloids. Such are copper, 
gold, silver, platinum, and others ; but these may occur 
mechanically mixed or in alloy with one another. Platinum 
is found in this way commonly associated with osmium and 
iridium, while native gold is nearly always alloyed with 
silver. 

The metal may be combined with sulphur or with some 
rarer element (arsenic, tellurium, antimony, bismuth, etc.), 
when it is known as a sulphide, arsenide, etc., of the metal. 
When combined with chlorine, bromine, iodine, or fluorine, 
a chloride, bromide, iodide, or fluoride is formed. An ex- 
tremely common group of ores is that of the oxides, where 
oxygen in different proportions is united with the metal, and 
there may be several oxides of the same element. These, as in 
the case of many other compounds, may be hydrous or anhy- 
drous, according as they have water in combination or not. 
When a metal is combined with silica (Si0 2 ), a silicate is 
formed. The group of silicates is extremely large, including 
many of the important rock-forming minerals, but as ores 
they are of little importance. Most of the silicates are 
extremely complex (hornblende, mica, feldspar, etc.), form- 
ing the group of bisilicates, but the few ores in this group 
are unisilicates, or minerals where only one metal is combined 
with the silica. When sulphur is in the place of silicon (S0 3 
instead of Si0 2 ), the sulphates are formed, and when in place 
of this there is carbon (C0 2 ), carbonates result. Aside from 



COMMON ROCK AND VEIN-FORMING MINERALS. 17 

these there are certain rarer compounds, the phosphates, 
arsenates, borates, etc., which are of little importance as ores. 

Common Veinstones. — Ores considered from the economic 
standpoint occur in beds or in veins. Usually they are 
associated mechanically with other minerals, sometimes rocks, 
which are of no economic value, and are known as gangue or 
veinstone. Almost any mineral may occur as gangue, and 
frequently there are several, some of which may be ores, 
such as iron pyrite, which are not of economic value. The 
most common veinstones are quartz, calcite, 1 fluorite or fluor- 
spar, and barite or heavy-spar, the first two being by far the 
most common. Many rarer minerals also occur as a part of 
the gangue in mineral veins, and it is from these places that 
many of the cabinet specimens of minerals are obtained. 

Fluorite (CaF 2 ) resembles calcite somewhat, being usually 
white, or transparent, though often coloured, having a very 
perfect cleavage and a vitreous lustre. It is, however, harder 
and somewhat heavier than calcite, and does not effervesce 
with acids, so that it is easily distinguished. 

Barite (BaS0 4 ) has nearly the same characters as fluorite, 
but is strikingly heavy for a light coloured mineral, and one 
is attracted by its weight ; hence its name heavy-sjDar. 
This mineral, as well as the others, has a distinctive crystal 
form; but, since it occurs more commonly as a massive 
mineral, this character is usually not of importance. 

Common Ores. — Through these veinstones the ores are dis- 
tributed, sometimes uniformly, sometimes very irregularly. 
At times they are concentrated into layers, often they are 
disseminated. In one part of the vein the ore may be of one 
chemical combination, in another a different kind may be 
1 Quartz is described on p. 5, calcite on p. 9. 



18 ECONOMIC GEOLOGY OF THE UNITED STATES. 

found; and even different metallic bases may predominate 
in different parts of the vein. 

One of two methods may be adopted in a classification of 
the different ores, — the mineralogical, based upon chemical 
composition, or what may be called the economic, in which the 
basis of primary division is the metal which the minerals 
contain. The latter is adopted here, as in the later chapters, 
for the general groups ; and under each metal the different 
mineralogical occurrences of importance are mentioned for 
the following : iron, gold, platinum, silver, copper, lead, 
zinc, mercury, manganese, aluminum, tin, nickel, and anti- 
mony. The ores of cobalt and chromium are omitted here 
since they are not used as a source for the metal, but as 
minerals, and hence are considered under the previous group. 
The specific gravity of nearly all the ores is high, and will 
not be given unless it is exceptional. 

Iron occurs, as an ore, in a number of mineralogical asso- 
ciations, but chiefly in the form of an oxide. Native iron 
exists in meteorites, and also in Greenland in an eruptive 
basalt, but in none of these occurrences is it valuable as an 
ore. The ores of iron are usually marked near the surface 
by the yellow iron rust with which we are familiar in 
old iron. 

Iron pyrite, the sulphide of iron (FeS 2 ), is mined for the 
sulphur, not for the iron it contains, the combination being 
so refractory that all the sulphur cannot be removed with- 
out great expense. It is brass-yellow in colour, with a 
metallic lustre, and is too hard to be scratched with a knife. 
It grades into copper pyrite, but when there is much cop- 
per present the colour becomes more golden. Sometimes, 
though not commonly, gold occurs in iron pyrites in in- 



COMMON ROCK AND VEIN-FORMING MINERALS. 19 

visible grains. There are other forms of pyrite in which 
iron is a constituent with some other metal, but none are so 
common as the almost pure iron pyrite. 

Limonite (2 Fe 2 3 + 3 H 2 0), hydrous sesquioxide of iron, 
is a brown or yellow mineral sometimes very earthy, but in 
its pure form having a hardness about equal to that of steel. 
A number of mineralogical varieties are commonly included 
under this mineral, the entire series of hydrous sesquioxides 
of iron (including gothite, turgite, bog iron ore, etc.) 
being called brown hematite by miners. The series can be 
told from other ores of iron by the fact that their powder is 
yellow or yellowish brown, and this is best seen by testing 
the " streak " which is obtained by scratching the mineral on 
a piece of rough porcelain or white quartz. 

Hematite (Fe 2 3 ) differs chemically from limonite by 
the absence of water, and there is accordingly every grada- 
tion between the two, the rust of hematite being limonite. 
The red colour of soils is due to a hematitic iron, as the yellow 
colour is to limonitic iron. Hematite is harder than limonite, 
has a metallic lustre, and varies in colour from red to brown, 
or even black. Its streak is reddish brown, and this serves 
to distinguish it from limonite and magnetite, the streak in 
the latter mineral being black. There are four common 
varieties of this species, — (1) specular hematite, which has 
a brilliant metallic lustre, and which is called micaceous 
hematite when the structure is foliated; (2) columnar he- 
matite, where the structure is radiating and the lustre less 
metallic ; (3) red ochreous hematite, where the colour is red 
and the structure earthy ; and (4) argillaceous hematite (clay 
iron stone), when the earthy form is mixed with clay. 
Miners include under the name red hematite all those vari- 



20 ECONOMIC GEOLOGY OF THE UNITED STATES. 

eties having a red streak, and according to the form of the 
ore they give different names, such as flaxseed ore, fossil 
ore, etc. 

Magnetite (Fe 3 4 ) is always black, with a black streak, a 
metallic lustre, usually with a granular structure and con- 
choidal fracture. In hardness it cannot be scratched with 
the knife. A feature which distinguishes it from the other 
ores of iron is its magnetic property. 

Franklinite is almost identical in form and appearance 
with magnetite, but it is not magnetic, and differs chemi- 
cally in the possession of both zinc and manganese in addi- 
tion to iron. In this country it occurs in only one locality 
as an ore, and that is at and near Franklin Furnace, Sussex 
County, New Jersey. 

Siderite, the carbonate of iron (FeC0 3 ), is readily 
scratched with the knife, is light compared with other iron 
ores, and in colour varies from gray to brown. It very closely 
resembles a discoloured calcite, which in reality it frequently 
is, the calcium being replaced by a certain per cent of iron, 
and in pure siderite being completely replaced. 

Gold occurs in the earth in only two mineralogical forms, 
so far as known, one in association with tellurium, the other 
native, the latter being its typical occurrence and the one 
from which the gold in use is obtained. While we speak of 
it as a native ore, this is not strictly true, since gold is 
nearly always alloyed with other metals, chiefly silver, in 
greater or less proportions. It is found mixed mechanically 
with other minerals such as iron pyrite, copper pyrite, and 
silver ores, and much of the gold is obtained from the last 
two sources, being a by-product in the extraction of the 
other metals. 



COMMON ROCK AND VEIN-FORMING MINERALS. 21 

Platinum occurs as an ore in the native form, but, like 
gold, usually alloyed with other metals, chiefly iron, iridium, 
and osmium. It is found in irregular lumps, usually of 
small size, is steel-gray in colour, has a metallic lustre, can 
be scratched with the knife, and has an extremely high 
specific gravity. 

Silver is found in much greater variety of chemical com- 
binations than the two last metals, since it is much more 
readily attacked by the ordinary mineralizers. Native silver 
is less common than the mineralized species, but it is, never- 
theless, not uncommon. It also occurs native as an alloy 
of gold, copper, and other metals, and much silver is annu- 
ally obtained from these sources. A large part of the supply 
of silver of this country comes from the sulphide of lead, 
where silver at times replaces some of the lead. There 
are numerous ores of silver, but only three are of marked 
importance. 

Argentite (Ag 2 S) is a blackish lead-gray mineral with 
metallic lustre, and distinguishable from the other ores of 
silver by its malleability. The argentiferous lead sulphide 
may be considered a mixture of this mineral and lead sul- 
phide, the richness in silver varying with the proportion of 
argentite. 

Pyrargyrite, or ruby silver, is a sulphide of silver with 
antimony and sometimes arsenic. Its colour is black, some- 
times a very deep red, and always with a ruby-red streak. 
The lustre is very brilliant metallic. 

Cerargyrite, or horn silver (AgCl), is extremely soft, 
and can be cut with a knife like horn. The colour is usu- 
ally gray, and the lustre resinous. With a very low heat 
the chlorine is driven off and native silver left. This ore is 



22 ECONOMIC GEOLOGY OF THE UNITED STATES. 

found in the Cordilleras, Mexico, and South America, in 
the latter place, particularly in Chili, occurring with a bro- 
mide and iodide of silver. 

Copper is found native in this country chiefly in the Lake 
Superior region. Its most common occurrence, however, is 
as the sulphide, chalcopyrite (CuFeS 2 ), or copper pyrites, 
which is in reality a sulphide of iron and copper combined, 
the proportion varying from an exceedingly cupriferous 
variety (chalcopyrite) to pure iron pyrites. The former is 
golden yellow in colour with commonly an iridescent tar- 
nish; the latter is brassy. Another sulphide, chalcocite 
(Cu 2 S), is lead-gray and rather soft. The oxide cuprite 
(Cu 2 0) is red in colour and translucent, with a metallic 
lustre, sometimes brilliant, sometimes earthy. Chrysocolla, 
the silicate (CuSi0 3 + water) is green to bluish green, the 
colour of copper rust. The lustre is vitreous, the specific 
gravity low, and the mineral soft. There are two carbo- 
nates of copper, — malachite (Cu 2 C0 4 + water) and azurite 
(Cu 3 C 2 7 + water), — the first being green in colour, the 
second blue, and each with brilliant vitreous lustre, of low 
specific gravity, and with a hardness such as to admit of its 
being easily scratched with the knife. Ores of copper are usu- 
ally more or less oxidized at the surface, and can generally 
be told in such places by the characteristic green or blue rust. 

Lead does not occur native, but is most commonly found 
in the sulphide galenite, or galena (PbS), a lead-gray mineral, 
with a metallic lustre and well-defined cleavages. The knife 
scratches it easily. Galena is very commonly argentiferous, 
and a considerable percentage of our silver is extracted from 
this ore. The sulphate of lead, anglesite (PbS0 4 ), is white, 
yellowish, or grayish, soft, and has a resinous lustre. 



COMMON ROCK AND VEIN-FORMING MINERALS. 23 

Cerussite, the carbonate (PbC0 3 ), has usually a white or 
grayish colour with a brilliant vitreous lustre, and is 
easily scratched with the knife. Both the sulphate and the 
carbonate are commonly the result of the decomposition of 
some other form of lead ore, usually galena, and all of the 
lead ores are frequently marked at the surface by a peculiar 
pale yellow rust. 

Zinc occurs most commonly as zinc blende, or sphalerite, a 
sulphide (ZnS), called by miners black jack. It varies 
markedly in colour, but is most frequently brown or yellow ; 
it has a peculiar resinous lustre which is quite distinctive ; 
it can be scratched with a knife, is rather light for an ore, 
and has very marked cleavage. There are two oxides of 
zinc, franklinite (already described under iron) and the 
red oxide of zinc, zincite (ZnO), which has a red colour, 
usually of a deep shade, though sometimes being orange- 
yellow, a brilliant vitreous lustre, and a hardness within 
the touch of the knife. Zinc as an ore occurs as a silicate 
in two forms, the hydrous and the anhydrous. The latter, 
willemite (Zn 2 Si0 4 ), is usually yellow with a vitreo-resinous 
lustre and a conchoidal fracture. As in most silicates, the 
specific gravity is low for an ore. The hardness is not 
great. Calamine, the hydrous silicate (Zn 2 Si0 4 + water), is 
white in colour, but otherwise resembles willemite, except- 
ing that it is lighter on account of the contained water. 
Smithsonite, the carbonate (ZnC0 3 ), is usually white or 
grayish, with a vitreous lustre inclining to pearly, and a 
hardness and specific gravity about like that of willemite. 
It effervesces with acids, as do many of the carbonates. All 
of the above ores of zinc, with the exception of franklinite, 
are translucent, or in some pure specimens transparent. A 



24 ECONOMIC GEOLOGY OF THE UNITED STATES. 

whitish rust is frequently present in zinc ores which have 
been exposed to the action of weathering. 

Mercury occurs as an ore in the form of the sulphide cin- 
nabar (HgS), although sometimes native mercury is formed 
by the decomposition of this ore, the affinity of the two 
elements being very slight. Cinnabar is very soft and 
heavy, has a brilliant lustre, is red in colour, often of a 
deep shade, and breaks with an uneven fracture. When 
heated carefully, the sulphur is driven off and metallic 
mercury is left ; but if heated too high, both the mercury 
and sulphur disappear. This ore is used not only as a source 
of metallic mercury, but also as a mineral for vermilion. 

Manganese occurs in many rocks as a black or purple stain, 
and it is an oxide of this metal which forms the arborescent 
stains called dendrites, which are so common on cleavage 
and jointed faces in many rocks. It is found very com- 
monly with iron in greater or less quantities ; and, as it is in 
iron-working that the chief supply of manganese is used, 
much of the metal is mined in this form and never sep- 
arated. There are, however, several ores which are mined 
for manganese, the principal being the three oxides, — pyro- 
lusite, psilomelane, and wad. Pyrolusite (Mn0 2 ) is usually 
black or dark steel-gray, with a metallic lustre, rather soft, 
and not very heavy. Psilomelane is a mineral of doubtful 
composition, being essentially an oxide of manganese and 
barium with water. Its characters are almost exactly 
like those pyrolusite, but it is much harder, and the 
knife scratches it with difficulty. Wad, or bog manganese 
(Mn0 2 + water), is usually impure, just as is the case with 
bog iron ore and for the same reason. It is extremely soft 
and earthy, not heavy, and varies in colour from dull black 



COMMON ROCK AND VEIN-FORMING MINERALS. 25 

to bluish or brownish black. The ores of manganese usually 
rust to this mineral under the action of weathering. 

Aluminum, although one of the most abundant of the metals, 
is also one of the most difficult minerals to extract from most 
of its ores, since it is firmly held in chemical combination by 
its mineralizers. It is found in all the silicates of alumina, 
of which there are many, and is present in all feldspars and in 
the clay or kaolin which results from their decay. Ordinary 
kaolin (H 2 Al 2 Si 2 8 + water) contains an inexhaustible supply 
of this metal, but it cannot at present be economically 
extracted. Corundum (A1 2 3 ) is a possible source of alu- 
minum, but is not now used, because it is more valuable for 
other purposes. Cryolite (Na 6 Al 2 F 12 ) is one of the chief 
sources of aluminum. It is usually pure white, though 
sometimes coloured, has a vitreous lustre, is translucent, 
brittle, easily scratched with the knife, and has a rather low 
specific gravity. It is fusible in the flame of a candle. The 
mineral bauxite (or beauxite) (Al 2 3 + iron and water), also 
used as a source of aluminum, is white or brown in colour, 
and occurs as concretions in clay. The colour and hardness 
vary with the per cent of iron. It is a comparatively light 
mineral. 

Tin is obtained entirely from the oxide cassiterite (Sn0 2 ), 
which is usually brown or black, with a brilliant lustre, a 
hardness too great to be scratched with a knife, and a high 
specific gravity. With the blowpipe, it can be reduced on 
charcoal with soda to metallic tin. The ore is found both as 
tinstone, in coarse granites or pegmatites, and as stream-tin, 
in river gravels, where, by the decay and removal of the tin- 
bearing rock, it has accumulated, owing to its high specific 
gravity and chemical indestructibility. 



26 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Nickel is obtained from the two sulphides, millerite, niccoli- 
ferous pyrrhotite, and the arsenide niccolite. Millerite (NiS) 
is a brass-yellow mineral, usually with a gray iridescent 
tarnish, a metallic lustre, and a moderately high specific 
gravity. It is brittle and can be scratched with a knife. 
Niccoliferous pyrrhotite is a sulphide of iron (Fe 7 S 8 ), with 
more or less nickel, and this ore is the principal source of 
nickel. In colour, it is bronze-yellow and copper-red, 
usually tarnished, and in specific gravity, hardness, and 
brittleness, it resembles millerite. In a fine powder it is 
attracted by the magnet. Niccolite (NiAs) is harder and 
heavier than either of the other two ores of nickel, being 
scarcely scratched with the knife. The colour is pale copper- 
red, with a gray or blackish tarnish, and a metallic lustre. 
Associated with nickel are the ores of cobalt, 1 and one of 
these ores, smaltite, contains nickel in varying proportions. 

Antimony and its compounds are obtained from the mineral 
stibnite (Sb 2 S 3 ), a soft, sectile mineral of medium specific 
gravity, a metallic lustre, and a lead or steel-gray colour, with 
a blackish or iridescent tarnish. It is soluble in hydro- 
chloric acid. 

-The above summarized description of minerals gives only 
those tests which can be applied roughly in the field without 
the use of exact methods, and includes those features which 
are present in ores, omitting the more purely mineralogical 
characters. The object of the summary, however, is less the 
presentation of the mineralogical than the geological features. 
There are many other minerals which one is liable to en- 
counter in the mines and quarries, some of them of economic 
value, but the above include the most common species, and 

1 Described above, p. 13. 



COMMON ROCK AND VEIN-FORMING MINERALS. 27 

the ores which are most liable to be met with frequently in 
economic work. Without a thorough mineralogical study, 
a more complete list or a more thorough statement of the 
features of the minerals would be useless ; but such a study 
is very desirable, indeed necessary for one who wishes more 
than an elementary knowledge of economic geology. 1 

!The most complete text-book on mineralogy is Dana's System of 
Mineralogy, though the essential features are given in the Text-Book or the 
smaller Manual of Mineralogy by the same author. Brush's Blowpipe 
Analysis gives the blowpipe tests for minerals. While there are numerous 
other text-books, these are the standard works and best adapted to the 
needs of the American student. 



CHAPTER II. 

EOCKS OF THE EARTH'S CRUST. 

The earth's crust, so far as it has been exposed to view by 
the processes of erosion, or by mining operations, is found to 
be composed of rocks of different characters, but all alike 
in the fact that they are composed of minerals. Sometimes 
a rock is composed of one mineral, but more commonly several 
combine to make up the rock-structure. Not only do they 
differ widely in mineralogical composition, but they differ 
both in form and in origin, and upon the latter basis we 
divide the rocks into three groups — Sedimentary, Eruptive, 
and Me tarn orphic. 

Sedimentary Rocks. — There is no single term which can 
properly be applied to those rocks which are neither eruptive 
nor metamorphic. The term sedimentary, strictly used, 
includes only those rocks which are formed as sediments, and 
excludes a large group of rocks subaerially formed. Stratified 
refers to those which are formed in strata or layers, but many 
metamorphic rocks are truly stratified; and, on the other hand, 
the glacial deposits are, in large part, neither sedimentary 
nor stratified. The terms fragmental or clastic might be used 
were it not for the fact that they exclude certain chemically 
deposited rocks, as well as those of organic origin, which are 
truly stratified. Of these several terms, sedimentary is, per- 
haps, the best general name, and in this treatise it will be used 
to include all rocks which do not fall into the other groups, 

28 



ROCKS OF THE EARTH'S CRUST. 29 

and the most important of which are both stratified and sedi- 
mentary. The material forming these rocks is of secondary 
origin, being derived either by mechanical or chemical means 
from pre-existing rocks. 

According to the nature of the material composing these 
strata we have a basis for classification. A conglomerate is 
composed of pebbles rounded, generally by water action, and 
cemented by finer, usually sandy particles, and some chemi- 
cally deposited mineral, such as calcite or iron oxide. The 
pebbly beaches are composed of material which might readily 
become consolidated into a hard conglomerate. When the 
pebbles are anguiar, as, for instance, when they have not been 
transported far from their source, the rock is a breccia. The 
name fault breccia is given to a similar aggregate of angular 
fragments found in a fault plane, and caused by the crushing 
of the rocks. As upon a beach there is every gradation from 
a mass of coarse pebbles to a fine-grained sand, so among the 
sedimentary rocks there is every gradation between con- 
glomerates and sandstones. The particles composing the 
sandstone are usually quartz, for the reason that this is 
the most durable of common minerals, and outlasts both the 
chemical disintegration and the mechanical wear to which 
the less durable minerals succumb in the process of weather- 
ing and transportation. Sandstone grades into clay rocks, 
which are composed of the finer parts of rock decay and 
of mechanical destruction. When consolidated these may 
become clay stones, or shales if they split easily in the direction 
of the bedding, and these may be sandy, or, on the other 
hand, of exceedingly fine grain. Since there are these 
gradations, it may be difficult to say whether a rock is a shale 
or a sandstone, and then it may be necessary to introduce 



30 ECONOMIC GEOLOGY OF THE UNITED STATES. 

a compromise term, such as shaly or argillaceous sand- 
stone, or sandy shale, according to the predominating 
constituent. 

These rocks are deposited in water, and in all bodies of 
water they are now being formed. The rivers, lakes, and 
oceans are repositories of these various materials, which are 
derived from the waste of the land. Frost and the agents 
of weathering cause the rock to disintegrate, the wind and 
moving glaciers grind the material finer; rain, gathering into 
rills, rivulets, and powerful rivers, sweeps this material toward, 
and finally into, the sea. Here the waves and currents work 
it over, grind it finer, and assort it, transporting the finer 
particles out to sea and depositing the coarser fragments near 
the land. The waves beating upon the shore batter off other 
fragments which are placed with those furnished by weather- 
ing and river erosion, and these all go to make up the sedi- 
mentary deposits of the ocean. These fragmental rocks are 
furnished by the land waste, and their source may be other 
sedimentary, or eruptive, or metamorphic rocks. 

Chemically Precipitated Rocks. — When rains fall upon the 
land, a part of the water sinks into the ground, while the 
remainder gathers into streams. The former, and to a slight 
extent the latter, takes from the rocks a certain store of 
soluble mineral which it carries away. In places, notably in 
inland seas, where this mineral matter becomes concentrated 
by evaporation, the water becomes overcharged, and is forced 
to precipitate some of the dissolved mineral. Carbonate of 
lime, particularly the magnesian carbonate, gypsum, and salt, 
are the chief deposits of this nature. In the neighbourhood 
of hot springs siliceous rocks and deposits of carbonate of 
lime may be precipitated ; but this class of rocks, since they 



ROCKS OF THE EARTH'S CRUST. 31 

are very local, is of scarcely any general importance in a 
consideration of the structure of the earth's crust. 

Organic Hocks. — Far from land, where rock fragments are 
rarely transported, the ocean bottom receives practically 
nothing but contributions of organic remains, excepting such 
fragments as may be transported by ice, or such bits of 
pumice as may float to that point. Minute lime-secreting 
animals furnish the greater part of this supply, and, therefore, 
in great ocean depths there is a muddy ooze, composed 
principally of their tests or shells, and this is called globi- 
gerina ooze, from the predominance of species of animals 
belonging to this genus. The chalk of England is a deposit of 
very nearly this character. In still greater ocean depths, even 
this small supply is not furnished; for here, owing to 
the great pressure of the water, the lime composing these 
shells is dissolved as they drop toward the bottom. Here a 
red ooze is formed, which is composed of the insoluble residue, 
and is therefore of extremely slow growth. Among the sur- 
face rocks, we have as yet failed to identify any similar 
stratum. 

Organic contributions to the strata are, however, more 
numerous than this. Practically, every sedimentary rock 
contains some relic of organic remains, even if no more than 
an indistinguishable powder of lime, resulting from the 
grinding up of calcareous shells. From this there is every 
gradation to pure limestone, when the entire stratum is made 
up of animal remains. Upon tropical coasts, where marine 
life attains a luxuriant development, there is frequently 
nothing furnished to the sea in solid form, excepting frag- 
ments of shells, corals, or other calcareous remains built up 
of carbonate of lime extracted from the sea-water by the 



32 ECONOMIC GEOLOGY OF THE UNITED STATES. 

marine animals. Such conditions prevail in coral-reef regions, 
where limestone beds are at present being deposited. There 
are conditions under which the limestone may be deposited 
in an impure form, as, for instance, by the addition of clay, 
forming an argillaceous limestone, or of magnesia, which 
produces a magnesian limestone. 

Certain minute animals (Infusoria) and plants (Diatoms) 
extract silica from the water for the construction of a 
siliceous test, and under certain conditions, chiefly in fresh- 
water deposits, these may be accumulated into a layer of 
infusorial or diatomaceous earth. Of coals little need be 
said here, since these strata will serve as a special topic. 
They have resulted from vegetable contributions to the 
earth's crust, under conditions favouring rapid burial and 
protection from destruction. Coals are of importance from 
an economic standpoint, rather than from their value as 
parts of the earth's strata; but, when carbonaceous shales 
and limestones are taken into account, it is found that 
vegetable contributions to the earth's crust are of much 
importance. 

Conditions of Accumulation. — These several deposits, most 
of which are extremely important in the structure of the 
earth's crust, although being formed in all bodies of water, 
are being most rapidly deposited in the ocean, where also they 
are most widespread. Hence it is that the sedimentary strata 
of the world are most commonly of marine origin. That this 
is true we know from their fossils, which are usually the 
relics of marine animals. Furnished by the decay of the rocks, 
or the death of animals or plants, these deposits are gathered 
in the sea and accumulated, often to great depths, before 
finally being raised above its surface. The earth's crust is 



ROCKS OF THE EARTH'S CRUST. 33 

changing in form : certain areas are slowly rising and others 
sinking. This we know partly by direct observation, partly 
by inference from the present position of sedimentary rocks 
on the very crest of mountains. If a coast line is suffering 
a gradual downsinking, the accumulating sediments may 
gather into a great thickness of strata, one deposited upon 
another. In places, thousands of feet of sediments have 
been thus accumulated. Those which are beneath become 
consolidated by pressure, and by a cement deposited from 
solution, by percolating water, and when finally the series 
of strata is elevated above sea-level, what was once an 
unconsolidated stratum of sand has been transformed into 
a hard sandstone. This, in general, is the way in which our 
sedimentary series has been formed and placed in the present 
position as a part of the land. 

In the ocean the fragments, being deposited by gravity, 
tend to build up layers of nearly horizontal strata, thicker 
and coarser near the shore, and thinning out as well as becom- 
ing of finer texture in a seaward direction. They vary from 
horizontality only when the irregularities of currents or 
waves cause a local variation of position, or when the form 
of the ocean bottom is uneven. Such cases are, compara- 
tively speaking, both rare and local, and it is a safe state- 
ment to make, in general, that sedimentary layers are 
originally horizontal. Yet, when these strata are found 
upon the land, they are scarcely ever perfectly horizontal, 
and are frequently tilted at a high angle. The same cause 
which brought about the depression and elevation of the 
ocean bottom, and which is still taking place, — namely, the 
contraction of the earth, — has caused the crust to wrinkle, 
the layers to bend and break, and mountains to form. Hence 



34 ECONOMIC GEOLOGY OF THE UNITED STATES. 

it is that we find the strata so often thrown out of the hori- 
zontal and cast into folds, or broken and faulted. 

Igneous Rocks. 1 — Rocks which have been formed by the 
cooling of molten material coming from within the earth 
are known as igneous. In some parts of the earth they are 
extremely abundant, while in others they are practically 
absent. Thus in the United States the Cordilleras abound 
in igneous intrusions and extrusions, while in the Central 
States they are very rare. In general, it may be said that 
igneous rocks abound in highly tilted strata, and are liable 
to be rare in those which are nearly horizontal. The same 
thing may be stated in another way ; namely, that igneous 
rocks are most abundant in mountainous regions, or in 
regions where mountains formerly existed but have been 
destroyed by erosion. Of the former the Cordilleras furnish 
an illustration ; of the latter, New England. 

Igneous rocks vary greatly in character in two ways: 
chemical composition and physical structure. On the one 
hand there are some having from sixty to seventy per cent 
of silica, on the other, forty per cent or even less, while 
between these two extremes there is every gradation in 
chemical composition. Accompanying this variation there 
is naturally a wide difference in mineralogical composition. 
There are, for instance, granites which have orthoclase feld- 
spar, quartz, and some other minerals; syenites containing 
the same minerals with the exception of quartz ; diorite car- 
rying hornblende and plagioclase feldspar ; and many other 
species, as will be seen in the accompanying table. 

In structural features these vary from glassy to coarsely 

1 A scientific treatment of the igneous rocks will be found in Rosenbusch's 
Mikroskopische Physiographie der Massigen Gesteine. 



ABSTRACT OF A 



TABULATION OF THE IGNEOUS ROCKS 
By F. D. Adams {Canadian Becord 







Alkali Feldspar 
Eocks. 

Orthoclase, Microline, 
Anortboclase, Albite. 


Alkali Feldspar 
Nepheline (or Leu- 
cite) Eocks. 


Leucite Eocks. 


Nepheline Eoci 




"With Mica, Amphibole, 
or Pyroxene. 


With Mica, Amphibole, 
or Pyroxene. 








"With 
Quartz. 


"Without 
Quartz. 




"Without 
Olivine. 


With 
Olivine. 


Without 
Olivine. 


Wit 
Olivii 


Abyssal 

(Plutonic) 

Eocks. 

Granular 
structure 


Granite. 
Biotite 

granite 
Hornblende 

granite 
Muscovite 

granite 


Syenite. 
Mica syenite 
Augite 

syenite 
Hornblende 

syenite 


Elseolite syenites 
Leucite syenites 










Effusive 

(Volcanic) 

Eocks. 


S 
O 

« 

bo 
« 
P 
o 


Quartz 
porphyry 


Quartzless 
porphyry 












Porphyritic 
structure 


Liparite 
Ehyolite 


Trachyte 


Phonolite 
Leucite phonolite 


Leucitite 


Leucite 
basalt 


Nephelin- 
ite 


Nephe 
basa 



The mineralogical character varies upon cooling according as the 
chemical composition of the molten magma varies. On the one extreme 
of the table the rocks are very acid, and the percentage of silica is very 
great. Accordingly free quartz occurs in these rocks, as, for instance, 
in the granites. From this extreme there is every gradation to the very 
basic rocks, of which the non-quartz and feldspar-bearing peridotites are 
illustrations. The granites frequently contain as high as seventy-five 
percent of silica, and sometimes more, whereas the rocks of extreme 
basic nature contain as little as thirty per cent. Since there is every 
gradation between these two extremes, it is natural to expect every 
gradation in mineralogical character, and such is the case ; for granites 



grade into syenites, and diorites 
rock between these extremes ai 
the basis of this variation the ftu 
classification depend. 

But some rocks reach the ki 
come to rest at considerable dep 
extremes there is every gradatio 
and rhyolite have essentially 
are given different names becau 
Granite cools slowly and hafl 
under conditions favouring til 



D UPON THE SYSTEM OE PROFESSOR H. ROSENBUSCH.' 

znce, December, 1891, pp. 463-469). 



.ILITE 
CKS. 


Lime Soda Feld- 
spar Nephellne 
(ok Leucite) 
Kocks. 


Lime Soda Feldspar Bocks. 


Bocks containing no 
Feldspar Constituents 
(Free from Alkalies). 






With Hornblende 
or Mica. 


With Augite, Diallage, 
or Hypersthene. 


Pyroxene 
Bocks. 


Olivine 
Bocks. 




Without 
Olivine. 


With 
Olivine. 


With 
Quartz. 


Without 
Quartz. 


Without 
Olivine. 


With 

Olivine. 








Theralite 


Quartz 
diorite 


Diorite. 

Mica diorite 

Hornblende 

diorite 


Gabbro 

and 
Norite 


Olivine 
gabbro 

and 
Olivine 
norite 


Pyroxenite 


Peridotite 








Quartz 
porphyrite 


Porphyrite 


Diabase. 

Augite 
porphyrite 


Olivine 

diabase 
Melaphyre 




Picrite 
porphyrite 


lilite 
asalt 


Tephrite 


Basantite 


Dacite 


Andesite 


Basalt 


Olivine 
basalt 







. All chemical varieties of 
from the earth, and upon 
principles of the Eosenbusch 



sd 



cool rapidly, while others 
)1 slowly, and between these 
quartz porphyry, liparite, 
;mical composition, but they 
ineralogical characters vary, 
itals, quartz porphyry cools 
of porphyritic crystals, and 



liparite may even be a natural glass so rapidly cooled that no crystals 
were formed from the magma. These are the principles upon which 
the above table is based. 

The dike rocks, considered by Eosenbusch intermediate between 
effusive and plutonic rocks, are omitted here, because there appears to 
be no especial basis for this division. The division into older and 
younger effusive rocks is also of doubtful value. 

Many subdivisions, such as the division of the andesites into mica, 
hornblende, hypersthene, and augite andesites, as well as a number of 
comparatively rare rocks, are omitted in this abstract. 



ROCKS OF THE EARTH'S CRUST. 35 

crystalline. Certain rocks are natural glasses, others have 
a glassy groundmass with large, quite perfect crystals, por- 
phyritic crystals, scattered through it, still others have a 
fine-grained granular structure called cryptocrystalline, and 
many are noncrystalline, or of a coarse-grained granitic 
structure. All of these various physical differences may be 
possessed by rocks having essentially the same chemical com- 
position, and, indeed, all may be present in the same mass. 
This difference in structure is largely the result of a differ- 
ence in the rate of cooling. A surface lava, cooling rapidly, 
may become a natural glass, because the minerals had not 
time to crystallize out of the molten magma, while the same 
lava, cooling slowly, might assume a granitic or holocrystal- 
line structure. 

Upon these two characters the following classification 1 
is based. Those in the . vertical columns are of essentially 
the same chemical composition, while in the horizontal rows 
the chemical variation is indicated by the change in minera- 
logical character. 

The position of these igneous rocks in the earth's crust 
varies. They differ from the sedimentary strata princi- 
pally in the lack of uniformity and regularity. So far as 
the chemical character is concerned, there is no uniformity of 
occurrence which can be predicted. Acid and basic lavas 
may be found intimately associated in the same region ; or, 
on the other hand, only one kind of lava may occur. Also, 
the igneous masses may all be of uniform structure, or there 
may be holocrystalline, cryptocrystalline, porphyritic, and 

1 Adapted from Adams' table, which is based upon the Rosenbusch clas- 
sification of igneous rocks. This table differs from the Adams table only in 
the omission of certain comparatively unimportant groups. 



36 ECONOMIC GEOLOGY OF THE UNITED STATES. 

glassy, all in the same region. This variability is the result 
of causes which cannot be discussed in detail here. In 
general, it may be said that lavas are derived from a portion 
of the earth some distance beneath the surface, and are an 
expression of an effort of this molten material to escape. 
If they are successful in this effort, they flow out upon the 
surface, cool rapidly, and tend to become glassy or crypto- 
crystalline in structure ; but if unsuccessful, they cool slowly, 
and become well crystallized. Their variation in chemical 
composition is apparently the result of a variation in source 
of supply, although it is difficult to explain why neighbour- 
ing volcanoes send forth different lavas, and still more diffi- 
cult to understand why the same volcano may at different 
times erupt different lavas. 

In the effort to attain the surface, some igneous rocks 
escape from the earth, and issue as lavas from a volcanic 
vent, or from a fissure. These extruded or effusive rocks may 
flow out quietly as lava, or, by the explosive violence of the 
contained water, they may be blown into fragments of 
volcanic ash or pumice. In both these cases there is a 
tendency to build up a cone about the vent, although, where 
the vent is a great crack or fissure, large areas of country 
may be flooded and no cone constructed. An ordinary 
volcano erupts lava which solidifies within a radius of a few 
miles from the vent, and its influence is therefore local ; but 
volcanic ash, rising high in the air, may float great distances 
either in the air or on the water. Later these deposits may 
be destroyed by denudation, and their fragments distributed 
in the ocean as sedimentary deposits ; or, on the other hand, 
they may themselves be buried without change, and become 
a part of a bedded series of sedimentary strata. 



ROCKS OF THE EARTH'S CRUST. 37 

While vast quantities of lava escape to the surface, vast 
quantities, also, are unsuccessful in their effort to escape. 
Such rocks are often found solidified in the other rocks into 
which they have been intruded. The volcanic vent, when 
the activity ceases, becomes clogged with the contained lava, 
and there is a plug or volcanic neck of solidified lava extending 
deep down into the earth. At times, the lavas find it easier 
to raise the strata in an arch than to break through them, 
and a laccolite, or well of lava, is formed. Intruded sheets of 
lava are found between the sedimentary strata, and at times 
these are rent asunder and masses of molten rock forced 
into them, forming great areas or bosses, such as the granite 
masses. These various rocks are said to be intruded or 
intrusive, and those like granite, which are intruded at 
great depths, are called plutonic or deep-seated. They are 
revealed only after the thick overlying layers have been 
removed. 

From all of these igneous masses, dikes, or narrow sheets 
of lava, may extend, sometimes as feeders, sometimes as off- 
shoots, and where the volcanic history has been complex, 
there may be a great complexity in character and position of 
the igneous rocks. They may cut each other, or traverse any 
of the groups of sedimentary or metamorphic strata. Some- 
times their boundaries are sharply defined and regular, but 
more commonly they are irregular, and even at times in- 
definite. It is more common for them to traverse the sur- 
rounding rocks in a more or less vertical sheet, but cases are 
numerous where such intrusions are nearly horizontal. 

For a study of that part of economic geology which deals 
with ore deposits, some knowledge of igneous rocks is neces- 
sary, for the reason that many such deposits are in greater 



38 ECONOMIC GEOLOGY OE THE UNITED STATES. 

or less degree due to their presence. By direct contact, 
these heated intrusions have, in some cases, caused an ac- 
cumulation of valuable ore. Still more commonly have they 
furnished the ore which has been gathered together in the 
vein; for nearly all, if not all, igneous rocks carry a certain 
percentage of the metals which, by the decay of the min- 
erals, may become a part of the sedimentary series, or which 
may be taken directly by percolating water and gathered 
into a vein. 

Metamorphic Rocks. — The third great group is classed as 
metamorphic. Originally these were supposed to mark an 
early stage in the history of the earth, possibly the original 
crust of the earth, and for some this may still be true, since 
they lie beneath the oldest known sedimentary strata, and 
when these were formed had their present character. They 
are the oldest known rocks, but to assume that they actually 
are the oldest is going farther than the facts warrant. Of 
late years, studies of these metamorphic districts have tended 
to withdraw from the old Azoic or Archean group many 
areas which were formerly supposed to be of this age. It 
is found that both sedimentary and igneous rocks may be 
made to lose their characters and become metamorphosed. 
This may happen by contact with large masses of plutonic 
igneous rocks, as well as in the centre of mountain chains, 
where the strata have been folded and crushed. The first 
is called contact; the second, regional metamorphism. As a 
result of this change, it happens that strata of much younger 
age than the true Archean may have very nearly the struc- 
ture of the Archean series. Parts of the New England hills, 
long classed as Archean, are now known to be of much later 
age. Whether the real Archean rocks owe their structure 



ROCKS OF THE EARTH'S CRUST. 39 

to the same cause, or whether the resemblance is one of 
coincidence, we are hardly in the position at present to state, 
although the tendency of the recent studies is toward the 
belief that they are the same in cause as well as in character. 

There is a wonderful variety of structure in the meta- 
morphic series. It might be said that every consolidated 
sedimentary layer is more or less metamorphosed. There is 
every gradation from the incoherent accumulation of coral 
debris to limestone and marble, from sandstone to its meta- 
morphic representative quartzite, and from clay shale to its 
representative among the metamorphics, slate and phyllite. 
These, in turn, grade into crystalline rocks so greatly meta- 
morphosed that the original condition cannot be determined. 
Leaving out of consideration these three groups which can 
be easily traced to their source, the crystalline metamorphics 
may be divided in general into two groups — gneisses and 
schists. A crystalline structure, often nearly as marked as 
in igneous rocks, is a common feature of these two groups, 
and they are alike also in the possession of schistose structure. 
In the schists proper, it is present in such a marked degree 
that the rock cleaves with facility in a given direction, while 
in the massive gneisses it is present only as a banding of 
some of the minerals, so that they frequently resemble very 
closely a granite. Other distinctions than that of schistosity 
are difficult to maintain, although it is common to find in 
schists a greater predominance of mica. 

A great number of sub-varieties of these metamorphics are 
known. We have, for instance, quartz schists, amphibole 
schists, mica schists, chlorite schists, hornblende gneisses, 
augite gneisses, and a large number of others ; but in all the 
foliated structure is the uniform and general feature. The 



40 ECONOMIC GEOLOGY OF THE UNITED STATES. 

minerals are arranged in bands, in strings, or, in some cases, 
simply with their major axes oriented in parallelism, and 
this gives the gneissic structure. Shales and slates are 
found passing over to chlorite schists, conglomerates and 
granites to gneisses or mica schists, and in all cases the 
direction of the schistose structure is at right angles to the 
direction of the pressure which is causing the metamorphism. 

Upon a study of the rock it is found that there are several 
ways in which this gneissic or schistose structure may orig- 
inate. It may be the result of the crushing of the com- 
ponent minerals and their arrangement in parallel bands ; 
or it may be due to the stretching of some of the minerals 
which are so nearly plastic that they do not crush ; or, finally 
and most commonly, it may be due to the development of 
new minerals, the result of heat, pressure, and attendant con- 
ditions. These facts may be verified by observation and 
study, and in many cases it is possible also to observe the 
cause for the metamorphism, as, for instance, when the strata 
occur in the core of a mountain chain. Both the igneous 
and sedimentary series furnish the material upon which 
metamorphism acts, and it is found that the same kind of 
metamorphic may be produced from sources as opposite in 
character as igneous and sedimentary rocks. This result, 
which at first thought seems an anomaly, is easily under- 
stood when we consider that a conglomerate may have the 
same chemical composition as a granite, or a shale as a 
diorite. Metamorphism takes account of material available 
rather than the particular form of this material, — of the 
chemical rather than the structural features. 

While it is possible that the old Archean series may rep- 
resent the original crust of the earth, either in its original 



ROCKS OF THE EARTH'S CRUST. 41 

condition or else altered by metamorphism, yet, since the 
same kinds of metamorphics are known to be produced by 
simple and easily studied and comprehended changes in 
known rocks, it is natural that one should be skeptical of 
an explanation which has for its support merely hypothesis. 
It seems probable that the great mass of Archean strata will 
be found to be metamorphosed sediments and eruptives, just 
as many similar but more recent gneisses and schists are 
known to be, although so far all efforts to prove this have 
been futile. 

Geological Age of Rocks. — In a study of the rocks and 
their relations one to another, it is necessary to have some- 
thing more upon which to base our studies than their mere 
chemical and physical characters. It is desirable to be able 
to refer to them according to age, and to differentiate 
between a shale formed in the first ages of the earth's history 
and one formed in more recent periods. It was at one time 
thought that such a classification in general was possible 
upon a mineralogical basis ; but more extended studies have 
shown that there is no uniformity of this sort, but that in 
any age strata of the same mineralogical composition are 
liable to be formed. 

Age of MetamorpMc Hocks. — Naturally the basis for a 
classification of rocks according to age must be a study of 
their relations one to another in the field. If one sedimen- 
tary layer is found resting on another, it seems probable that 
the lower layer is the older. In the case of eruptives and 
metamorphics this is not necessarily so. The bedding of a 
metamorphic rock may be mere schistosity of secondary ori- 
gin, and hence of no value in determining the relative age 
of the layers. In the true Archean rocks a certain time- 



42 ECONOMIC GEOLOGY OF THE UNITED STATES. 

classification has been made out in places ; but it is of local 
value only, and so far no valid grounds for extending it have 
been found. This much is known, however, that a certain por- 
tion of the metamorphic series, the greater part apparently, 
belongs to the lowest and oldest geological period. So far as 
we know no fossils exist there, no sedimentary layers are 
found among them, and all known sedimentary and fossil- 
bearing strata are of later origin. 

Age of Eruptive Rocks. — With eruptive rocks, we are in 
no way better able to construct a chronology. Locally, it is 
possible in most cases to determine the relative age of 
associated eruptives, or of the erupted rock, and the 
one through which it passes ; but this cannot be extended 
beyond the locality where it is observed, because in any 
part of the earth's crust, or in any period, any kind of an 
igneous magma may have been erupted. Still, if the igneous 
mass cuts a certain other rock, it is the later of the two, and 
so far we have a chronology ; but only a hundred years ago, 
a dike may have cut an Archean series, and to-day we would 
be unable to tell whether it were a hundred years old, or 
many ages. Sometimes, by a careful study of a region, it is 
possible to determine quite accurately the age of an igneous 
mass. Thus in the eastern United States great dikes of an 
igneous rock, diabase, are found cutting the strata of all ages 
from the earliest down to the time of the Triassic period, but 
nowhere crossing the later layers. The age of these lavas is, 
therefore, Triassic. At times, an igneous rock is in such 
a position in the stratified series that one is unable to tell 
whether it was formed at the same time as these, or later; 
that is, whether it flowed out as an extrusive lava sheet, 
while the sediments were being formed, or whether it 






ROCKS OF THE EARTH'S CRUST. 43 

were later intruded between the layers. If intruded, it may 
follow the bedding planes very closely, though it may cut 
from one layer to another, which would not be the case 
if extruded. An intruded sheet would show the effect of 
heat at both the upper and lower contact, and would be 
liable to intrude dikes into the overlying layer. An extruded 
lava would not produce these effects, but the sedimentary 
layer above would probably contain fragments of the lava. 
These are about the only means of determining the age 
of an eruptive, although it may be added that if a rock is 
coarsely crystalline and granitic, it is usually old, for such 
masses are intruded into the earth at considerable depths, and 
are not revealed until the overlying layers are removed, which 
is usually a slow process. In very high mountain regions, 
where erosion is rapid, and in the case of thick lava flows, 
there are exceptions to this rule, so that it is only of very 
general application. 

Age of Sedimentary Mocks. — There is a much more satis- 
factory chronology for the sedimentary strata, the rocks which, 
so far as revealed, predominate in the earth's crust, although 
in years we can make no estimate at all approximating the 
truth. By the folding of the mountains in Pennsylvania, 
and by the erosion of the streams which have breached them, 
there are found to be revealed not far from 40,000 feet of 
sedimentary strata, one layer upon another. These were all 
deposited in water, and apparently under the same laws 
which govern the accumulation of sedimentary deposits to- 
day. This must have represented a vast lapse of time, yet 
there are represented here less than one-half of the total 
thickness of the geological column from the Archean to the 
present. Evidently this period of time must be estimated in 



44 ECONOMIC GEOLOGY OF THE UNITED STATES. 

millions of years, but how many it is impossible to say, and 
those who have hazarded guesses have made estimates 
ranging from ten to several hundred millions of years. 
There are no facts upon which to base such an estimate, 
because the conditions are too variable, and our knowledge 
of them entirely too obscure. 

Knowing, however, that one layer is above another, and is 
hence later, we have a valuable local indication of relative 
age and, as far as a given stratum, or a group of strata, can 
be traced, the chronology is correct. But it is possible to 
extend this chronology even beyond the limits possible by 
directly tracing a given series of layers, for it is found that 
in these sedimentary strata there are fossils, relics of animal 
and plant life of the time when the rocks were formed. The 
fauna and flora of the world to-day are marked by a general 
uniformity of character, certain groups of animals and plants 
predominating, which give character to the life of the period 
as compared with those which preceded. Assuming that 
this has been the case in the past (and this is more than a 
mere assumption, for it is verified by a study of the fossils), 
an examination of the fossil contents gives us a chronology 
which, in its broadest features, is of world-wide application. 
Before a certain series of rocks was deposited, there were no 
vertebrated animals, then fishes appeared, then reptiles, and 
mammals, and birds. If, now, in a certain stratum the petri- 
fied bone of a bird is found, it can be affirmed definitely that 
this stratum belongs to a period later than the time of 
appearance of the first birds. A knowledge of the exact 
species of the bird might even indicate the exact period. 
Certainly, this, taken together with a knowledge of other 
fossils from the same bed, would furnish a means of identifi- 
cation of this bed as a part of a general group. 



ROCKS OF THE EARTH'S CRUST. 45 

The knowledge upon which our ability to make these 
determinations is based has been slowly acquired by a long 
and careful study of many different fields, and, as far as the 
general groups are concerned, it is a safe statement to make 
that ordinarily a knowledge of the fossil contents will serve to 
place a certain stratum in its proper position in the geological 
time-scale. This study has proved that there has been a 
development, an evolution of forms, from simple to more 
complex, and that, in each succeeding age, the prevailing 
types of life are progressively higher. In some places, the 
divisional line between two ages is indefinite and difficult to 
draw, but generally it is sufficiently well defined for the 
purposes of division. New types seem, at times, to have 
developed rapidly, and to have displaced the older types, in 
a period of time so brief that the gradation is not marked. 
Yet, in various parts of the earth, every gradation, generally 
speaking, is found. The division into ages is usually based, 
however, upon fields where no gradation exists, but where 
the dividing line is sharp, and these places are generally 
regions where for a time sedimentation was interrupted. 
That is to say, a region of marine deposit was transformed 
to dry land for a period of sufficient duration to admit of 
the development of new types, and then a submergence 
brought these animals into the condition of fossils in beds 
above the earlier ones 1 (Fig. 1). Having been demonstrated 
for such a place, the observation can be extended to other 
areas. 

For the minor details of the geological time-scale, the 

classification is less satisfactory. Just as at present the 

fauna of Australia is widely different from that of America, 

so in the past, contemporaneous deposits, even when not far 

1 This is known as an unconformity. 



46 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



removed geographically, may have entombed widely different 
species. While the presence of certain types of mammals, 
chiefly man, would serve to indicate the general contem- 
poraneity of the deposits of Australia and America, it is 
quite unlikely that, from a study of the fossils alone, the 
two deposits, of exactly the same age, would be placed in 
the same minor subdivision in the scale. Recognizing this, 
geologists rarely attempt to correlate the subdivisions of an 
age in different regions, but confine their use to local areas. 




Fig.,1. — Unconformity. The inclined strata were deposited and tilted before 
the horizontal strata were laid down. Between the time of deposit of the 
tilted strata and that of the horizontal, several geological ages may have 
elapsed. 

Thus the term Silurian is used in all countries, but the sub- 
division Niagara is a local New York term, and indicates a 
part of the Silurian, whose position in the New York column 
is perfectly definite, and whose fauna is practically uniform. 
How far such a term can be extended, even on the same 
continent, depends upon a variety of circumstances, but, 
generally speaking, its use is local. 

The stratified rocks are divided, according to these 
features, into a chronological series of large divisions of a 
general nature, and subdivisions of local nature. In the 
table which follows, the American terms are given, and no 
attempt is made to correlate these with their probable equiv- 
alents in other countries. 



ROCKS OF THE EARTH S CRUST. 



47 



Q 


QUATERNARY J 


Recent 




O 
N 
O 
fa 


(Age of Man) 


Pleistocene 




TERTIARY 2 
(Age of Mammals) 


Pliocene 




Miocene 




o 


Eocene 3 




O 


CRETACEOUS 


Laramie 






Upper Cretaceous 




Lower Cretaceous 




H 2>p§ 


JURA-TRIAS 


Jurassic 




E 


Triassic i 






CARBONIFEROUS 

(Age of Plants) 


Permian 






Coal Measures 






Lower Carboniferous or 
Sub-Carboniferous 






DEVONIAN 
(Age of Fishes) 


Catskill 






Chemung 


Chemung 5 




Portage 




Hamilton 


Genesee 




Hamilton 




Marcellus 




Corniferous 


Corniferous 


Q 


Schoharie 


o 


Canda-Galli 


N 


to 

la 

fa £ 

AC 

fcD 
3 


UPPER 
SILURIAN- 


Oriskany 




^ 


Lower Helderberg 




hi 

S3 


Sallna 




Niagara 


Niagara 




Clinton 




Medina 




LOWER 
SILURIAN 6 


Trenton ■ 


Cincinnati 




Utica 




Trenton 




Canadian 


Chazy 




Quebec 




Calciferol! s 




CAMBRIAN 


Upper Cambrian 7 




Middle Cambrian 






Lower Cambrian 














ALGONKIAN 


Keweenaw an 8 






Upper Huronian 






Lower Huronian 






ARCHEAN 


Laurentiax 
(Fundamental Complex) 





1 There is a tendency in some directions to substitute the term Pleistocene for Quaternary. 

2 The United States Geological Survey adopts the term Neocene to include the Pliocene 
and Miocene. 

3 In Europe, the subdivisions of the Tertiary are particularly well marked, and a fourth 
division, Oligocene, is recognized as occurring between the Eocene and Miocene. 

4 The term Newark is now used by the United States Geological Survey to include the 
strata of the eastern states, which were formerly called Triassic. The Jurassic and Triassic 
periods are not well developed in America. 

(For continuation of notes, see following page.) 



* 



48 ECONOMIC GEOLOGY OF THE UNITED STATES. 

The above table gives the best recognized names for the 
most prominent members of the geological column. Minor 
subdivisions are introduced only in the case of the New York 
Devonian and Silurian. Each period contains many minor 
subdivisions based upon local studies, and, in the Cretaceous, 
for instance, the names for the minor subdivisions of the 
Atlantic coast series differ from those of the central 
N Ks - western states, and these in turn are different from the 
names applied to the Cretaceous strata of the Pacific coast. 
The subdivisions are therefore of local value only, and will 
' be learned by a study of localities. 

Disturbance of the Rocks. — While in places the surface of 
the earth is composed of sedimentary rocks in orderly suc- 
cession, one above another, and in a very nearly horizontal 
position, there are large areas where they lie in very much 
disturbed positions. The earth is apparently losing heat 
and, in consequence, contracting, the outer crust endeavour- 
ing to accommodate itself to the constantly decreasing size 
of the interior. It is, consequently, wrinkling very much as 
an apple wrinkles by the loss of water as it dries. Speaking 
broadly, and without entering into the discussion of the 
various theories, this seems best to account for the con- 
tinental and mountain folds of the earth's crust. 



5 Some of the minor divisions or epochs of the Devonian and Silurian are introduced here, 
because they are well developed and well worked out in New York state. 

G In England, the term Ordovician is used as the equivalent of Lower Silurian, and the name 
Silurian is confined to the upper division, but this has not been generally adopted in this country. 

7 This division of the Cambrian is more perfectly developed in Europe than in the United 
States. 

8 This division of the pre-Cambrian rocks is based on the Lake Superior region, where these 
strata are better exposed and more fully studied than in any other part of the country. The 
Archean includes those rocks which show no sign of clastic origin, and have no indications 
of organic remains. Algonkian includes the strata between the true Archean and the true 
Cambrian. They show signs of sedimentary origin, and, when more carefully explored, may 
yield fossils. The rocks are distinctly older than the Cambrian, and also markedly younger 
than the Archean, which may be in part the original crust of the earth. 



% v ^ 



ROCKS OF THE EARTH'S CRUST. 49 

As a result of this process, portions of the land are rising, 
others sinking, with reference to the datum-plane of sea- 
level. It is because of these changes that the great thickness 
of sedimentary rocks is possible. Of the 40,000 feet of such 
strata in the Pennsylvania column, the greater number are 
rocks formed not far from the shore lines. Such a vast 
accumulation under such conditions proves a long-continued 
sinking of the sea-bottom at this point. The fact of the 
existence of these marine rocks at present above sea-level 
points conclusively to a subsequent upheaval. A study of 
the region has proved that, from the Cambrian to the close 
of the Carboniferous period, the sea-bottom sank ; then 
followed an elevation, and since that period this elevation 
has been maintained and even added to, although the actual 
elevation has been reduced by the long-continued erosion to 
which the area has been subjected. 

Such changes in relative position of land and sea are 
among the most common phenomena with which the geologist 
has to deal. Not only have they taken place in the past, but, 
even at the present time, they are being registered along 
the coast lines, as slow movements of the land, just as in 
the past. The presence of peat bogs and submerged forests 
beneath sea-level, and of beaches and wave-cut cliffs above 
the present shore line, is recorded on many coasts; and if 
more evidence is needed, it is necessary to state merely that, 
on the coast of Sweden, man himself has recorded the pres- 
ence and amount of these changes by actual observations 
upon fixed bench-marks. 

At times the land is bodily uplifted, forming plains or 
plateaus, according to the amount of uplift. In such cases, 
although elevated above sea-level, the rocks retain their 



50 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



original horizontality. If the uplift is unequal, the rocks 
may break along a given plane, and upon one side move 
higher than on the other, forming a fault, — a dislocation of 
the rocks accompanied by differential movement. The 
fault plane may be vertical, or it may dip, or hade, one way 
or the other. The side which is the higher is called the 
upthrow side, that which is lower the downthrow, without 
regard to which side has actually moved. A fault in which 
the hade is toward the downthrow is called a normal fault 
(Fig. 2); where toward the upthrow, a reverse fault (Fig. 2), 
and here a vertical shaft will pierce the same stratum twice, 




V ' Ft 

Fig. 2. — Cross-section showing normal fault (N) , vertical fault ( V) , and reverse 
fault (R). AB, downthrow ; BC, lateral throw. 



once on each side of the fault plane. Where the fault plane 
is nearly horizontal, or nearly parallel to the bedding, it is 
called an overthrust fault, because by this means earlier 
strata may be thrust over upon later strata. When the 
horizontal direction of a fault plane is in the direction of 
the dip of the strata, the fault is a dip fault ; when at right 
angles to this, a strike fault (Fig. 3). 

Folding of strata is even more common than faulting, for 
even the most rigid of rocks may bend when the pressure 
of the overlying rocks is sufficient to prevent them from 
breaking. A simple upfold of the rocks is an anticline 



ROCKS OF THE EARTHS CRUST. 



51 



(Fig. 3) ; a downward fold is a syncline (Fig. 3) ; and a 
single rise, followed by a horizontal or nearly horizontal 
condition of the strata, is a monocline. The direction in 
which the rocks pitch into the earth is the dip, and the 
angle of dip is the angle made by this plane with the 
horizontal. The strike is a horizontal line at right angles to 
the dip and in the plane of the dip, or the strike is the 
horizontal direction of the outcropping stratum. Folding of 
rocks in mountains may be of one or all of these simple 
types, or it may be complicated by faulting, or the folding 
itself may be extremely complex. At times the rocks are 




Fig. 3. — Section showing anticlinal (A) and synclinal folds (B), overturned 
folds (C), and a strike fault (D). 1-2, direction of dip. 



folded so far that they become overturned, in which case 
older strata appear to lie upon younger, and a careful study 
is necessary to detect the cause. The folds themselves may 
be folded, and all of these complications added to the in- 
trusion of igneous rocks, the metamorphism of sedimentary 
strata, and the subsequent erosion of the area, gives to us an 
extremely complex maze of rocks. It is in such places that 
mines are commonly located. 1 

1 This brief statement of such geological facts and principles as seem 
absolutely necessary for a comprehension of the elements of economic 
geology might be advantageously supplemented by a thorough course in 
geology. The reader is referred to Geikie's Text-Book of Geology, Geikie's 
Class-Book of Geology, Jukes-Browne's Physical Geology, Dana's Manual 
of Geology, or Le Conte's Elements of Geology, for a complete presentation 
of the subject. C^J^ y fc % 



CHAPTER III. 

PHYSICAL GEOGRAPHY AND GEOLOGY OF THE UNITED 

STATES. 

Theee are five geographical zones in the United States : 
(1) the southern coastal plains; (2) the mountains of the 
eastern states ; (3) the inland plains and plateaus of the 
central western and southern states ; (4) the Lake Superior 
hilly region, a southern extension of the Canadian Highlands ; 
(5) the Cordilleran region, including the Rockies, Sierra 
Nevadas, and Coast ranges, with their enclosed plateaus and 
basins. These are capable of much more minute subdivision, 
but this will serve as a general classification upon which to 
base the summary which follows. 

Coastal Plains. — There are several distinct parts to this 
area, all of which, however, are marked by the possession of 
the general features of a plain extending inward from the 
coast line, and composed of recent strata. The Quaternary 
Coastal Plains, or coastal plains proper, a subdivision of 
this general region, are the most recent additions to this 
country ; being, in fact, old sea-bottoms, so recently elevated 
above sea-level that in many places the fossils entombed in 
their strata are the same as the living species in the neigh- 
bouring ocean. The rocks here are horizontal, or nearly so, 
and consist of the usual materials formed along shore lines. 
Sandstones, clays, and conglomerates predominate, and while 
in some places the strata are partly or completely consoli- 
dated, for the most part they are still incoherent deposits. 

52 



PHYSICAL GEOGRAPHY AND GEOLOGY. 53 

Their origin has been partly from the action of waves upon 
the old shore line, partly from river deposits assorted and 
distributed by the oceanic waves and currents. Just such 
a deposit is being formed near the shore in these same 
regions at present. 

The coastal plains, which exist in New Jersey as a narrow 
strip and are not found north of this state, increase in size 
toward the south, until in Texas they have a width, in places, 
of from forty to fifty miles. It is proper to include here, 
also, the delta and lower flood plains of the Mississippi, which 
are in part the elevated deposits of this river, formed in a 
great estuary, in part the flood plain deposits of the river 
formed since the elevation of the region. In topography, 
these plains are extremely simple. Where they attain their 
best development, in Texas, they are exceedingly young, so 
young, in fact, that a perfect system of drainage has not yet 
been established upon them. There is a monotonous stretch 
of dead level plain, relieved only here and there, where some 
stream, extending out from the interior, has sunk its channel 
to a slight depth in the strata, and furnished a drainage 
sufficient for the growth of trees. Between the streams 
there are flat-topped divides, swampy, and occupied by a 
growth of un nutritious swamp grass, because undrained. A 
few small streams have begun to develop in the areas between 
the extended streams, but as yet very little progress has been 
made. Skirting this plain on the seaward side is a strip of 
varying width, in which new land is being made. Bars are 
being thrown across the river mouths by the combined action 
of tides, waves, and winds ; lagoons are being formed, and 
these are being filled with sediment and by the growth of 
marsh vegetation. 



54 ECONOMIC GEOLOGY OF THE UNITED STATES. 

This region is at present of very little economic impor- 
tance, for the reason that it is inaccessible. What stores 
of clay there may be below the surface, or what local deposits 
of iron, or even of lignite, where streams have brought down 
vegetable matter, can only be conjectured by a comparison 
with the similar deposits formed in the age immediately pre- 
ceding this, and at present existing in the region immediately 
to the landward. At present the only economic products in 
the region are the sands along the shore. 

Florida Plains. — Florida, which forms a part of the 
general region under consideration, is a unique geographic 
unit. It is a region of Tertiary, essentially calcareous rocks 
built upon a submarine bank whose origin is not clear. 
Being situated in the warmer waters, coral growth was 
possible ; and in this respect it differs from the other por- 
tions of the coastal plains, where the ocean water was 
freshened and clouded with sediment by the influx of river 
water. As Florida was, at the time of its construction, 
practically unaffected by land water, so also to-day we find 
no land streams extending across it. The drainage is that 
of newly developed streams, and the short time that they 
have been in possession of the land, together with other 
causes, has prevented them from draining the peninsula 
perfectly, and, consequently, immense swamps and shallow 
lakes exist as a feature of this geographic form. Since 
the streams of the Florida region are practically sediment- 
free, coral growth is still possible upon the shore and upon 
the off-lying banks, so that, by this means, added to the 
influence of the mangrove tree, which grows with its roots 
in the salt water, the coast of Florida is growing outward. 

Tertiary Coastal Plains. — While the coral beds of the 



PHYSICAL GEOGRAPHY AND GEOLOGY. 55 

Florida peninsula were being developed, the coast line of 
the southeastern states was some distance farther inland 
than at present. This condition did not exist in New 
England, excepting in the off-lying islands ; but from New 
York, southward to the Rio Grande, the land was lower, 
and, in general, the submergence increased to the south- 
ward. The submerged strip in Texas reached inland nearly 
as far as Austin, the present lower course of the Rio Grande 
was a great estuary, and an extensive embayment extended 
well up the valley of the Mississippi. Apparently the 
coastal conditions were not unlike those at present pre- 
vailing, and the deposits are just what we know to be 
forming along the present shore line. These strata have 
been uplifted without folding or extensive faulting, but are 
inclined gently seaward, giving a slight tilting with an in- 
creasing elevation inward. 

Cretaceous Coastal Plains. — In the immediately preceding 
period, the Cretaceous, the geography of the country was 
vastly different from the present, the Rocky Mountains not 
having then been formed, and their area being, in large 
part, occupied by oceanic water. The far west was separated 
from the east by an arm of the ocean, and in all these areas 
of water Cretaceous deposits were formed. There is no 
genetic difference between the plains formed in the west 
and those which are found skirting the eastern base of 
the Appalachians, but it will be necessary to divide these 
two areas and include the Texas Cretaceous with the other 
central and southern plains, and for the present consider 
only the Cretaceous deposits east of the Mississippi. The 
eastern coast line was still lower than in the Tertiary, which 
followed, and coastal plains were formed, remnants of which 



56 ECONOMIC GEOLOGY OF THE UNITED STATES. 

are still found skirting the inner margin of the Tertiary 
Coastal Plains at Martha's Vineyard, Long Island, in parts 
of eastern New Jersey, in central Alabama, and north- 
eastern Mississippi, as well as elsewhere along this line. 
They are, for the most part, scarcely more disturbed, though 
slightly more consolidated than the Tertiary. 

In these Tertiary and Cretaceous plains, the clays are 
usually still plastic, and the sands frequently only partially 
consolidated ; but the coral rocks of the Florida region are 
more indurated, because calcareous rocks are easily consoli- 
dated by the action of percolating water. This series of rocks 
is prolific in certain classes of economic deposits. The clays 
of the Cretaceous and Tertiary in New Jersey and elsewhere, 
and the phosphate deposits of the South Carolina and 
Florida districts, are of primary importance ; and in Texas 
there are extensive beds of lignite and of iron ore, while in 
Louisiana valuable salt deposits occur. 

Triassic Coastal Area. — Between these two plains and the 
mountains, there are two intermediate areas, one composed 
of the older Palaeozoic strata, forming the foot hills and the 
eastern plateaus of the Appalachians, the other an area of 
Triassic strata, which may be considered under the general 
division of the eastern plains, although, in reality, they 
belong to a type of their own. What the conditions were in 
Triassic times, it is not easy to say, nor can it be stated how 
extensive the Triassic deposits were. The strata existing at 
present are chiefly sandstones and conglomerates of shore 
line, or, as in the case of the Connecticut valley area, of 
estuarine origin. Local areas occur in the south; there is 
an extensive area in Pennsylvania and New Jersey, forming, 
in the latter state, the undulating plains between the High- 



PHYSICAL GEOGRAPHY AND GEOLOGY. 57 

lands and the Cretaceous plains ; and in the Connecticut 
valley there is an area extending from the Sound to the 
northern part of Massachusetts, narrowing toward the north, 
where, in the Triassic period, the head of a bay was situated. 

During Triassic times, and also shortly afterwards, there 
prevailed in the region under consideration a period of 
volcanic activity, the last one to which the region east of the 
Mississippi has been subjected. Great flows of lava were 
poured out upon the surface in the Connecticut valley and 
New Jersey; and, both at this time and later, dikes of trap 
or diabase were intruded across the strata as well as between 
them. The period of volcanic activity was widespread, and 
the character of the erupted material moderately uniform 
from North Carolina to Nova Scotia. Not only were the 
Triassic strata themselves cut by these traps, but all the 
older rocks in the neighbourhood were also traversed, even 
to a considerable distance from the Triassic. With the 
beginning of the Cretaceous age, these eruptions ceased. 
The trap hills near Patterson, New Jersey, the Palisades of 
the Hudson, East and West Rock at New Haven, the 
Hanging Hills of Meriden in Connecticut, and Mt. Hol- 
yoke in Massachusetts, are all witnesses of this period of 
vulcanism. 

Partly on account of the great age of the strata, partly as 
the result of the volcanic intrusions, and partly because the 
rocks have been subjected to folding and faulting, the sand- 
stone of Triassic age is compact and well consolidated. 
When the texture is even, and the colour reddish brown, 
owing to the presence of iron, the sandstone of this age is 
of value for a building-stone ; and its importance for this 
purpose is greatly increased by its nearness to the market. 



58 ECONOMIC GEOLOGY OF THE UNITED STATES. 

There are also metalliferous deposits in the Triassic at the 
contact of the igneous rocks, but these are usually of but 
very little value. 

Mountains of the Eastern States. — This area is divisible 
into two important geographic units, the Appalachians and 
the older Archean mountains of New England, which also 
extend southward, east of the Appalachians, and northward 
into Canada. 

The Eastern Archean Mountains. — This area is a region 
of hills and low mountains, worn down to their very core, 
and consisting of rocks chiefly of metamorphic or of igneous 
origin, with here and there areas of Palaeozoic strata. The 
region has had an exceedingly complicated history. It, 
together with a large portion of eastern Canada, consists 
chiefly of Archean rocks which, before the beginning of the 
Palseozoic era, were folded into a series of mountain folds 
of extremely complex structure and attitude, being even 
then composed of metamorphic and igneous rocks of the 
same character as the strata which at present constitute 
their mass. Since then they have been again folded so as 
to include Palseozoic rocks. This was a part of the land 
which furnished the sediment out of which the rocks of the 
Appalachians are constructed, and in this area must be 
included, not only much of eastern Canada and New Eng- 
land, but also the Adirondacks, the Highlands of New 
Jersey, and the low Archean hills east of the Appalachians 
in Pennsylvania, Maryland, and the more southern states. 

The exact history of this area cannot be presented, but it 
is composed of distinctly igneous rocks (diorites, granites, 
syenites, etc.), and of metamorphic rocks, whose origin is 
uncertain, but which may be, in part, altered sedimentary 



PHYSICAL GEOGRAPHY AND GEOLOGY. 59 

strata. At the beginning of the Cambrian period, not only 
were these rocks much folded, faulted, and metamorphosed, 
but also they were much denuded. The old Cambrian shore 
line can still be traced in places, as in the Adirondacks and 
on the western margin of the New Jersey Highlands. A 
new period of mountain growth occurred during the Palaeo- 
zoic, presumably at the time of the growth of the Appa- 
lachians, for all the rocks included in these mountains are 
included here also. Apparently the folding was more intense 
in New England than in the Appalachians, since, by its 
action, the Palaeozoic strata have in places been meta- 
morphosed almost beyond recognition, while in the Appa- 
lachians they have not lost their character. It is probable 
also that the mountains were higher here, and that igneous 
rocks were again intruded into the mountain cores, and in 
places caused to flow out upon the surface. Be this as it 
may, we have, in the New England area and the northern 
and southern continuations of it, an extensive mountain 
region worn down to its very core, and revealing to us rocks 
which are apparently as old as any on the earth's surface. 

Owing to its complex history and structure, there is, in 
this region, a great diversity of economic deposits. There 
occur here great areas of granite, of marble and slate, 
deposits of iron, and, in small quantities, practically all the 
metalliferous deposits. For reasons to be suggested later, 
the metalliferous minerals are not generally accumulated 
here in great abundance. 

Appalachian Mountain Region. — The Appalachians proper 
are folded rocks of Palaeozoic age. No later strata are in- 
cluded, because the mountains had practically ceased growing 
when these were deposited ; and no earlier rocks are found 



60 ECONOMIC GEOLOGY OF THE UNITED STATES. 

in the Appalachians proper, because erosion has not been 
carried to a sufficient depth to reveal the underlying plat- 
form, excepting to the east, where the Palaeozoic strata were 
perhaps thinner and the mountains higher. Both to the 
north and the south the folds of the Appalachians die out, 
and on the western side they become lower, and finally 
merge into the plateau of the central states. 

In these mountains, the topography is dependent upon the 
rock structure. The strata have been thrown into great 
waves or folds, sometimes sharp, sometimes broad, and usually 
pitching in the direction of their axes, which are nearly 
parallel to the trend of the mountains. The rocks are 
alternating sedimentary strata, with varying hardness and 
with a variable dip, usually at a considerable angle to the 
east or the west. Owing to the long continued erosion to 
which these mountains have been subjected since the close 
of the Carboniferous, the variations in hardness have had a 
marked influence in determining the topographic features. 
Where hard sandstone or conglomerate beds outcrop there 
are hills ; and the valleys are usually located in the lime- 
stone belts, although some streams flow directly across the 
strike of the strata, and cut at right angles both the hard 
and the soft layers. The hills are linear, with their axes 
parallel to the mountain folds, and they often follow the 
irregularities of the outcropping strata, as these turn in 
passing from one fold to another. 

This district furnishes us with much building-stone, slate, 
marble, iron, petroleum, nearly all the anthracite, and much 
of the bituminous coal of the country, as well as many other 
valuable materials in smaller quantities. The importance of 
mountainous districts, as producers of valuable ores, is due 






PHYSICAL GEOGRAPHY AND GEOLOGY. 61 

chiefly to the fact that the rocks are folded, so that erosion 
reveals a great variety of strata, and that in mountains the 
conditions which favour the accumulation of such deposits 
are present; namely, the formation of cavities and the 
presence of eruptive rocks. The Appalachians are sur- 
prisingly free from eruptive rocks, while faults and cavities 
are much less frequent there than in the Rocky Mountains, 
so that the greater importance of the latter region as a 
producer of metals is easily understood. It is possible that 
the old New England mountains, at the time of their greatest 
development, simulated more closely the Rocky Mountains 
than do their smaller neighbours the Appalachians. 

Central Plains. — Very nearly one-half of the country is 
included in this area. Commencing at the western margin 
of the Appalachians, where the rocks cease to be thrown into 
waves or folds, there is a series of plateaus and plains 
extending westward to the base of the Rocky Mountains and 
southward to the Gulf of Mexico. Already those portions 
of the plains which form the marginal and coastal areas 
of the east have been described. The portion which remains 
consists of Cretaceous and Palaeozoic strata chiefly, although 
in Nebraska and vicinity the rocks were formed in a great 
inland sea of Tertiary age. Considering the area as a whole, 
the strata are very nearly horizontal, and the country a plain 
scored and eroded to a greater or less degree in different 
places, so that at times its character as a plain is almost 
destroyed. 

The geology is by no means as simple as might be inferred 
from this statement. At different points, rocks of nearly 
all ages outcrop at the surface, and the present condition is 
the culmination of a complex history of elevation and sub- 



62 ECONOMIC GEOLOGY OF THE UNITED STATES. 

mergence. The essential features of the entire region are the 
almost complete absence of igneous rocks, and the fact that 
the strata have been uplifted without marked disturbance. 
These statements must, however, be qualified, since in several 
places the strata are disturbed and igneous rocks are present. 
There is a broad gentle fold, in Ohio and the neighbouring 
states, known as the Cincinnati arch. In Missouri, a knob of 
igneous rock projects through the Palaeozoic strata at Pilot 
Knob. A large area in Indian Territory and Arkansas has 
been extensively folded and subjected to igneous intrusion ; 
and the same is true of a smaller region in Central Texas, 
northwest of Austin. The Black Hills also form an igneous 
and folded area in the midst of the plains, and there are 
other similar areas elsewhere. Some of these disturbed 
regions, as those of the Black Hills and Indian Territory, are 
actual disturbances in the plains; but others, as Pilot Knob, 
are islands of pre-Palseozoic age. These regions, though 
considerable in number, are small in extent when compared 
with the plains as a whole. Properly, they should be con- 
sidered separately ; but, in this generalized statement, they 
need only be mentioned as disturbances in the great area of 
almost universally horizontal rocks. 

These strata, being practically undisturbed by folding, 
faulting, or volcanic intrusion, are not such as would be 
expected to }deld up large stores of metallic wealth, yet much 
zinc and lead and some iron come from this area, while salt, 
gypsum, coal, petroleum, and gas, are found in great quan- 
tities in various parts of the region. The major part of the 
rocks are well-consolidated limestones, sandstones, and shales, 
so that in this area there is an almost inexhaustible supply 
of the non-crystalline building-stones. 



PHYSICAL GEOGRAPHY AND GEOLOGY. 63 

Lake Superior Region. — In northern Michigan, Wisconsin, 
and Minnesota, there is a region of metamorphic rocks, a 
southern extension of the Canadian series, which, like those 
of New England, have had an extremely complicated his- 
tory. Here there is a central core of complex Archean sur- 
rounded by later rocks, among which are late Archean, 
Algonkian, and Cambrian strata. This has been a moun- 
tainous region ; but, unlike New England, it has not been 
subjected to intense Palaeozoic folding, although since the 
first period of mountain-building there has been considerable 
folding and faulting, accompanied by the intrusion and 
extrusion of igneous rocks. It is now a hilly region, much 
less mountainous than New England, but, like this province, 
is an old mountain worn down to its roots. From here 
are obtained immense quantities of copper and iron, and 
in this area there are large stores of building-stones. 

Cordilleran Region. 1 — Toward the close of the Cretaceous 
there existed, in the area now occupied by the Cordilleras, a 
great sea with archipelagos, and perhaps even continuous 
masses of land, composed of older rocks. An extensive dis- 
turbance of the strata, which has not yet ceased, was then 
initiated. This disturbance extended from Alaska to 
southern South America, and, although in places the moun- 
tains are still growing, the disturbance has now passed its 
maximum, and is declining. In the course of its develop- 
ment the rocks were extensively faulted and folded, igneous 
rocks were intruded into the strata, and numerous volcanoes 
poured out floods of lava and quantities of volcanic ash 

1 Only for the purpose of a general statement can such a comprehensive 
term be allowed. This is in reality a very complex province, composed of 
several geographic units. 



64 ECONOMIC GEOLOGY OF THE UNITED STATES. 

upon the surface, while during ail this time erosion was at 
work attempting to wear away that which was elevated. 
The present Cordilleras have resulted from this complex 
interaction of forces. 

All ages of strata, from the Archean to the Pleistocene, 
are included in this region, and very nearly every variety of 
rock is found there. By the folding, chains and ranges were 
built, and valleys formed between them, some of these being 
great basins and extensive plateaus. At first many of these 
valleys, including parts of the Great Basin, were partially 
enclosed seas, and finally lakes with an outflow to the sea ; 
but, as the enclosing mountains grew higher and the climatic 
conditions changed, these became transformed into interior 
basin lakes, then salt lakes, and in many cases they eventu- 
ally became completely desiccated. The deposits of these 
seas and lakes were in part incorporated in the later moun- 
tain folds, but the most recent of them still remain hori- 
zontal strata of gravels and clays, forming great flats 
between the mountains, often with no drainage to the sea. 

In this region there exists very nearly every economic 
product of the earth's crust. There is probably no region 
of similar extent in the world where such a variety and 
abundance of mineral wealth is stored. Already in develop- 
ment it exceeds any other portion of the earth in the output 
of many metals, and its resources are only partly understood. 
The more valuable and better known substances only have 
been discovered, and of these there undoubtedly remain 
many yet to be found. There is, also, in this province a 
vast store of mineral wealth known to exist, but at present 
undeveloped on account of its inaccessibility and remoteness 
from the market. Among these may be mentioned building 



PHYSICAL GEOGRAPHY AND GEOLOGY. 65 

and ornamental stones, clays, gypsum, salt, coal, and iron. 
The metals, such as gold, silver, lead, and copper, which 
are of sufficient value for transportation come chiefly from 
this region, and their output is increasing every year. 
Nature seems to have conspired to produce here the proper 
conditions for the accumulation of a great variety of valuable 
minerals in great abundance ; and what would otherwise 
have been an uninviting and sparsely populated region has 
become, in consequence of this prodigality of nature, a well- 
populated region. 

Summarized Geological History of the United States. 

This in general states the geological features of the several 
provinces of the country. The history of its development 
may be inferred from this statement, but it seems well to 
supplement it by pointing out the main steps of this evolu- 
tion; to put in a summarized form the sum of our knowledge 
of the geological evolution of the country as a whole and of 
the grander geographic features. 

What the condition of the country was during the earliest 
geological ages is only obscurely understood ; but since that 
time the history becomes progressively more clear. That 
there was land, however, is shown by the fact that sedi- 
mentary rocks were formed. It is evident that there were 
land areas in the eastern seaboard states, in Canada, the 
Lake Superior province, and in parts of the Cordilleras ; but 
how extensive, or exactly where they were, cannot be stated. 
Besides these there were probably other Archean land areas, 
now destroyed, and buried beneath the later strata. 

In Canada, and in some of the seaboard states, such as 



66 ECONOMIC GEOLOGY OF THE UNITED STATES. 

New Jersey, the Archean seems to be divisible into two dis- 
tinct groups of rocks, an older and a younger, the latter 
being derived from the former ; and in places there is some 
ground for a still further subdivision. There is no part of 
the Archean in the country which is better understood than 
that of the Lake Superior province. Here there is a central 
core of Archean of great complexity, an old mountainous 
land area, from which were derived immense quantities of 
sedimentary material of pre-Cambrian age, which, although 
since then greatly folded and faulted, is still much less dis- 
turbed than any area of similar age in this country, so that 
its true and original composition can still be determined. 
It is, therefore, of great value as an indication of the condi- 
tions of that period. From a study of these rocks it is found 
that, as in many areas of more recent strata, both sedimen- 
tary and eruptive rocks occur, that a vast lapse of time was 
occupied in their formation, and that during this time moun- 
tain-folding and other orographic changes were in progress. 
Probably the history of this region was not distinctly unlike 
that of other Archean areas less easily studied. 

At the close of the Archean, there were many land and 
probably mountainous regions in the country. There was a 
very large area extending from Labrador to Lake Superior, 
and thence northwestward toward the Arctic, besides certain 
areas in this country, as mentioned above. At present, the 
rocks of Archean age outcrop where they have been uncov- 
ered from beneath later strata, or perhaps, in places, as in 
some parts of Canada, where they have never been buried. 
Where they are now found we know that they existed ; but 
how far they extended, and how many extensive areas of 
former land are now buried beneath the ocean, or beneath 



PHYSICAL GEOGRAPHY AND GEOLOGY 67 

later rocks, will probably never be known. The Archean 
rocks were highly metamorphosed in most places even in 
pre-Palseozoic times, though they have undoubtedly under- 
gone some changes since then ; and into these strata granitic 
and other igneous rocks were intruded in Archean as well 
as in later periods. 

Around the margins of this land Cambrian sediments were 
accumulated. Such places show that shore lines existed not 
far from the seaboard of New England and also on the west- 
ern side of the New Jersey highlands, indicating an island 
of considerable linear extent extending southwards from 
New England. A shore line skirted a part of the Adiron- 
dacks; and there were shore lines on the southern margin 
of the Lake Superior Archean region, in Texas, and in 
parts of the Cordilleras. The probable geographic condi- 
tions, indicated by these shore lines, were a series of islands, 
mountainous and generally linear, marking, in a very rough 
way, the merest outlines of the developing continent. The 
backbone of the Laurentian highlands in Canada was the 
most prominent land area ; and linear islands or groups of 
islands extended along the eastern coast and in the Cor- 
dilleras, their greatest length being, in general, parallel to 
the present mountains of these two regions. Probably other 
islands existed, and perhaps the extent of the islands just 
described was really much greater than has been stated. It 
is an interesting fact that the present valley of the St. Law- 
rence was then a strait between New England and the 
Laurentian Archean land areas, the valley being thus early 
indicated. It is also worthy of note that the present valley 
of the Mississippi was a sea partly enclosed on three sides, as 
at present, and that the eastern and western enclosing areas 



68 ECONOMIC GEOLOGY OF THE UNITED STATES. 

sketched, roughly, the present though much later-formed 
mountains. 

During the remainder of Palaeozoic times, — that is, until 
the close of the Carboniferous, — the event of chief impor- 
tance was the accumulation of vast quantities of sediment in 
the seas surrounding these land areas and furnished from 
their destruction by weathering and erosion. There must 
have been a slow and long-continued subsidence of the sea 
and a long-continued and vast destruction of the land areas. 
The sediment was furnished to the sea, where now the Appa- 
lachians exist, from a land area which probably extended 
seaward beyond the present eastern coast line. In the Cor- 
dilleras the events are less well determined. 

Toward the close of the Palaeozoic, much of the region of the 
Appalachians and of the central states became shallow water 
arid marshy land, upon which the coal vegetation flourished ; 
and the same is probably true of some parts of the Cordilleras. 
Immediately following this came the great revolution which 
culminated in the formation of the Appalachians and the 
elevation of the central states above sea-level, — an eleva- 
tion which has been maintained since then, with occasional 
oscillations, but continuous elevation above the sea. The 
Jura-Trias ages were of little importance in the evolution 
of the eastern part of the continent, although some changes 
took place in the Appalachian district, the most important 
being an increased elevation accompanying the volcanic out- 
bursts which caused the traps of the Palisades, the Connect- 
icut valley, and elsewhere. In the west, however, this 
period was marked by the growth of the Sierra Nevadas and 
the addition of much land to that part of the continent. 

At the beginning of the Cretaceous the outline of the 



PHYSICAL GEOGRAPHY AND GEOLOGY. 69 

continent was tolerably well determined, and only finishing 
touches were necessary to complete its present form. The 
Pacific bathed the base of the Sierras, the Coast Range not 
then being formed ; and along the eastern margin of the con- 
tinent the ocean covered the eastern part of all the states 
from New Jersey to Georgia. Florida, the greater part of 
Alabama, Texas, and Arkansas were beneath the ocean, and 
an arm of the sea extended northward, along the line of the 
Rocky Mountains and the states east of them, beyond the 
confines of this country. Islands existed in this mediter- 
ranean sea, in Texas, Arkansas, Indian Territory, Dakota, 
and probably elsewhere, while in the Sierras arms of the 
ocean formed estuaries, or in some cases had been shut in to 
form lacustrine basins. The country east of the Mississippi 
was nearly completed, excepting for the addition of the 
coastal plains; but the western region was yet to be per- 
fected. 

During the Cretaceous period sediment accumulated in 
these inland seas and along the continent margin ; and at 
its close the great inland sea was transformed to a dry land 
area with many lakes. The Coast Range was not then 
formed, nor were the Rocky Mountains more than begun. 
To the eastern coast a slight addition was made, but the 
Tertiary plains were yet unformed, and the Gulf of Mexico 
extended as an arm of the sea up the valley of the Missis- 
sippi for a considerable distance. 

During the Tertiary period the Coast Range was devel- 
oped, and vast floods of lava were poured out upon the 
surface. The Rocky Mountains were also formed then, 
and by these mountain-foldings great lakes were caused, 
partly in the Cordilleras, partly on the eastern margin. In 



70 ECONOMIC GEOLOGY OF THE UNITED STATES. 

the Rockies also vast quantities of lava were erupted, and 
this period of volcanic activity is only just now, within recent 
geological times, brought to a close. The great Cordilleran 
lakes existed even into the Quaternary period, but most 
of them have been drained, while some were destroyed 
by mountain-folding and the lake sediments built into the 
mountains. Even now, however, some of the lacustrine 
basins exist as interior basins, although because of the 
aridity of the climate, they are not now occupied by water. 
The Great Salt Lake is a shrunken remnant of such a lake 
in a great basin. 

By the close of the Tertiary period the southern and east- 
ern coast was nearly completed, though in Quaternary 
times a slight addition has been made, particularly in the 
south. Two notable areas have been added to this coast, 
one the delta and flood plain of the Mississippi, the other 
the Florida Peninsula. Both of these areas, which form a 
part of the coastal plains, were formed partly by material 
deposited and partly by the elevation of the land. 

At the close of the Tertiary period the land, in the north 
at least, was considerably higher than at present, and during 
the immediately succeeding period, the Pleistocene, the 
northern part of the continent, as far south as New York 
and Cincinnati, was covered by an ice sheet which has some- 
what modified the topography and the drainage, partly by 
its erosive effect, but chiefly by means of the detritus which 
it has left scattered over the surface. This period, like all 
which preceded, has had its effect upon the economic 
resources of the country. It has given to us many of the 
brick clays, it has changed the character of the soil, often 
disastrously, and it has given us the lakes and waterfalls 



PHYSICAL GEOGRAPHY AND GEOLOGY. 71 

which abound north of the southern margin of the glacial 
drift. Accompanying its presence there was a subsidence of 
the land in the north, which has transformed pre-existing 
river valleys into the estuaries and harbours which have been 
so influential in giving the northern states such importance 
in commerce. 

This is, briefly, and without entering into details or proofs, 
the general evolution of the continent. Its form was 
roughly sketched in the very earliest period and it has 
been slowly perfected, although undoubtedly many changes 
yet await it. No adequate mention has been made of the 
effect of erosion during all this time, but this is of prime 
importance. Old lands have been worn down and the ruins 
deposited in the water to afterwards be again built into land 
and perhaps again transformed into sediment. Erosion and 
sculpturing have been ever-acting, and the present form of 
the continent is the resultant of the conflict between the two 
opposing forces ; the one tending to build up, the other to 
tear down. 



CHAPTER IV. 

ORIGIN OF ORE DEPOSITS. 

Original Condition. — Deposits of ore are accumulated 
under certain conditions which favour the gathering together 
of like kinds of minerals in concentrated form. It will be 
found, as the later pages are studied, that there are many 
diverse ways in which this accumulation is brought about, 
and that it is possible to offer a classification of ore deposits 
based upon origin. 

What the original condition of metals and metalliferous 
deposits may have been cannot be said. There are some 
who believe that the interior of the earth is, in part at least, 
composed of unoxidized metals, and that the ores which we 
find in the rocks are, in reality, the form assumed by these 
elements when they reach the surface, and come under the 
influence of the surface conditions, where oxidizing com- 
binations are prevalent. Be this as it may, igneous rocks, 
which bear to the surface the substances existing below the 
surface, contain in their mass a greater or less proportion of 
metals in mechanical or chemical combination. It requires 
no careful analysis, nor even a microscopic study, to detect 
iron and, frequently, manganese, in the form of their oxides, 
in these eruptive rocks. Sometimes, copper salts and other 
metalliferous compounds are present in sufficient quantities 
to be detected by the eye. Analyses have for a long time 
shown that rarer metals are present in small quantities in 

72 



ORIGIN OF ORE DEPOSITS. 73 

many eruptive rocks ; and very careful analyses of certain 
rocks, made for the purpose of determining the point, have 
shown that rare and precious metals are present. They seem 
to be more prevalent in the complex basic bisilicates, such 
as augite and hornblende, and hence the basic rocks (diorites, 
diabases, etc.) are more prolific producers of these metals 
than are the acid rocks. 

It is to Sandberger 1 that we owe the first proof of these 
facts, although his experiments have been repeated and 
extended by others. Previous to the time of his observa- 
tions, analyses of rocks had not revealed any but the more 
common metals ; but by separating the olivine, hornblende, 
mica, etc., and analyzing these, he proved the existence of 
iron, nickel, copper, lead, zinc, tin, cobalt, and other metals. 
Since this study, nearly all metals have been found in the 
common minerals in appreciable quantities. Nearly all lithia 
micas contain tin ; muscovite, although poor in other metals, 
usually contains copper ; and black micas carry many metals. 
Sandberger also found the disseminated metals in slates, and 
he proved also that the veinstones might all be derived from 
the common rocks ; for even fluorine is found in mica and 
barium in feldspar, while the other necessary elements are 
common enough. 

Sedimentary strata, being all formed from material either 
directly or indirectly derived from igneous rocks, naturally 
contain these metals also, and the same holds true for meta- 
morphic rocks. In other words, metals are disseminated 
through all rocks, being much more prevalent in some than 
in others, but generally being in such small quantities that 
only very careful analyses serve to prove their presence. 
1 Sandberger, Untersucliungen iiber Erzgange. 



74 ECONOMIC, GEOLOGY OF THE UNITED STATES. 

Removal of Original Ores. — In order to bring these metals 
into concentrated form, some agent is necessary to act as a 
carrier, and this agent is usually the ever-present water. 
All rocks contain water. In the quarry, it is shown by 
the loss of weight when the quarried block is exposed to 
the dry air; in the volcano, its presence is proved by the 
clouds of steam which rise from the lava stream, and the 
vesicles and cavities which it causes in the lava by its 
expansion. This water was partly built into the rocks when 
they were formed; but partly, probably chiefly, it comes 
from the surface. During every rain, a part of the fall 
flows off as surface water; a considerable portion creeps 
through the soil and reappears in springs; but a small 
portion starts on an underground journey, during which it 
often penetrates to great depths, traverses hard and soft 
rocks alike, and is ever present as interstitial water in the 
microscopic crevices in the rocks. 

Cold water, free from impurities, has little solvent power 
except for the most soluble minerals, such as salt, gypsum, 
or calcite ; but very little of the underground water is pure. 
As it passes through the soil and the surface coating of 
vegetable matter, certain acids and gases are absorbed. 
These give to the water an increased solvent power, and as 
it descends it may eventually become so strongly acid, or so 
alkaline, that even the most insoluble substances are taken 
into solution. The temperature of the earth progressively 
increases as the depth is increased, and hence water at con- 
siderable depths attains a temperature often high above the 
boiling-point, so that its power as a solvent is vastly in- 
creased. Even ocean water carries in solution small quan- 
tities of gold, silver, and most other metals, and it is probable 



ORIGIN OF OHE DEPOSITS. 75 

that, under conditions of great heat, the percolating water of 
the earth becomes a solvent of as great power as many of our 
acids and alkalies. Its effect is expressed not alone by the 
material carried in solution and subsequently concentrated, 
but also, in many places, by alterations of the rock-forming 
minerals by the extraction of certain parts, or the addition of 
others. This form of change sometimes results in the com- 
plete destruction of one mineral and the formation of another. 

Origin of Cavities. — Granting, as we must, that the im- 
prisoned water of the earth bears ore in solution in many 
cases, there remains to be considered the more difficult 
subject of the manner in which this ore is concentrated. 
Many of the ores occur in cavities where they have been 
deposited from solution. Sometimes these cavities are only 
partly filled ; at times they are completely filled ; and it is 
not uncommonly the case that the cavities are not only filled 
but enlarged, the force which causes the mineral to be 
deposited being so great that the walls of the cavity are 
spread apart b} r the growing deposit. 

Joint Planes (Plate II.). — The most numerous cavities 
are those formed by joint planes, cracks extending across the 
rocks in given directions and breaking them into blocks 
without any sensible motion or displacement. Joint planes 
are of two kinds, — incipient, or those whose presence is 
shown only when weathering develops them, and normal 
joint planes, which, even without the aid of weathering, are 
present as dividing planes in the rocks. They are of the 
same origin apparently, and differ merely in the amount of 
development. In igneous. rocks there are joints of cooling, 
the result of contraction by the loss of heat. The basaltic 
columns and the concentric, nearly horizontal joint planes of 



76 ECONOMIC GEOLOGY OF THE UNITED STATES. 

granite are illustrations of these. Sedimentary rocks are 
crossed by joints of contraction, due, perhaps, to the loss of 
water; for when these rocks are formed, a certain amount 
of water is built into their mass between the fragments, and 
this may be lost, causing a considerable contraction, when 
the strata are raised above sea-level and drained by erosion. 
There is, also, in these rocks a possible contraction due to 
the loss of heat; but whether this is often sufficient to 
account for joint planes is a question. The most common 




b 

Fig. 4. — Horizontal strata crossed by an irregular fault line, ab, which upon 
faulting produces cavities as in Fig. 4 a. 

cause of these divisional planes in sedimentary and meta- 
morphic rocks, and even in some igneous rocks, is contortion 
or folding, which causes stresses that are relieved by a frac- 
turing or jointing ; and hence all folded rocks are crossed by 
joints. These are generally nearly vertical; and two sets are 
commonly present, forming rhomboidal blocks, with angles 
frequently approaching the right angle and rarely very acute. 
Mineral veins are sometimes formed along these joints, which 
are channel-ways of easy passage for water ; and even where 
veins are absent, small deposits are frequently found. 



ORIGIN OF ORE DEPOSITS. 77 

Fault Planes. — During the folding of rocks there are 
often formed faults or dislocations where one side slips 
past the other. These faults, being of deep-seated origin, 
often extend to great depths, and serve as passage-ways to 
the surface for the heated waters from below. If the 
fault plane were a perfectly straight line, the cavity would 
not be very great; but most commonly the fracture plane 
is irregular, and a series of cavities are thus often pro- 
duced where two. concave walls come to rest opposite 



Fig. 4 a. — The same as Fig. 4, showing the result of faulting along an irregular 
fault plane, producing alternate cavities and closed spaces. 

each other (Figs. 4 and 4 a). By the motion of the rocks 
the uneven walls, rubbing against each other, tear off frag- 
ments, and produce in the vein a crushed substance, a fault 
breccia, which is common where two projecting parts of the 
vein are in contact. At times the faulting amounts to actual 
crushing, and the rocks are very badly brecciated. Such a series 
of cavities furnish an easy channel for the passage of water. 

Solution Cavities. — Water, percolating through soluble 
rocks, such as limestone, dissolves the minerals, and forms 
cavities or caves which may later be filled with ore. Such 



78 ECONOMIC GEOLOGY OF THE UNITED STATES. 

cavities are formed independently in some regions, but very 
frequently they have their beginning in joint planes ; and in 
faulted regions the water, which later served to fill the vein 
with mineral, may at first have dissolved cavities in the 
enclosing rocks. 

Minor Cavities. — Cavities exist in lava where there was a 
lack of supply of material, or, more frequently, where super- 
heated water expands into steam, and produces a pumiceous 
or scoriaceous lava. So, also, in sedimentary rocks there 
may be original cavities (usually on a small scale) where 
there was a lack of material, or where some soluble portion 
may have been dissolved after the formation of the rock, 
as, for instance, in or around fossils. The contact of sedi- 
mentary and igneous rocks, or of two diverse series of 
strata, owing partly to the difference in character of the two, 
and partly to the presence of minute cavities, is a plane of 
weakness, along which the underground water finds a pas- 
sage. Also the more porous rocks, such as sandstone, form 
channels, as is proved by the fact that artesian wells are 
found in such strata when bounded above and below by 
more impermeable layers. Besides these, there are numerous 
other cavities of small size and minor importance. 

Classification of Ore Deposits. — There have been many clas- 
sifications of ore deposits offered, and attempts have been 
made to classify them upon each of the three following 
bases : (1) mineral contents, (2) form of deposit, (3) origin 
of deposit. The first, that based upon mineral contents, is 
far from satisfactory, since the ores of silver, copper, zinc, 
and many others are all found in the same form of deposit 
derived in the same manner. It is not scientific ; and yet in 
any economic study this must serve as a primary basis for 



ORIGIN OE ORE DEPOSITS. 79 

classification. An attempt to study ore deposits upon any 
other basis would involve much confusion, since it would be 
necessary to consider the veins of one class, as iron, for 
instance, then for the other metals in succession; and the 
study of any one metal would be scattered throughout 
various chapters. Therefore, as the primary basis for our 
study, we must adopt the metal. The more scientific clas- 
sification would discard the above and consider the relation 
of the ore deposit to its surroundings ; for if we have a vein 
of a particular form and origin, why should it be important 
whether it is one of lead or of copper, since both may be 
formed in the same way, and may even be present in the 
same vein? 

The great majority of classifications, apart from the eco- 
nomic, have been based upon the form assumed by the 
deposit rather than upon the origin. This, it seems, advances 
a matter of secondary importance to the first rank, and in the 
classification which is given here origin has been considered 
as of prime importance, and form of secondary importance. 1 
Carrying this scheme out to the end, and losing sight of 

1 Other classifications are discussed in various books upon economic geol- 
ogy and upon ore deposits, and will not be considered here. Some of the 
subdivisions in this scheme are taken from Whitney's classification, which 
is most currently accepted in this country, and is by far the best of 
any based upon the form of the deposit. The classification here given had 
been used for two years by the author in the class in economic geology at 
Cornell University before his attention was called to the fact that a similar 
classification was in use at the Houghton Mining School in Michigan. Its 
author, Dr. M. E. Wadsworth, published this classification in the early part 
of 1893 (Report of Michigan State Board of Geological Survey for 1891-92, 
p. 144. It was previously published in the Catalogue of the Michigan Min- 
ing School at Houghton), and so far as it coincides with this classification 
Dr. Wadsworth has priority, both of use and publication, although in the 
two cases the scheme was originated independently. 



80 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



the economic bearing, the character of the ore itself would 
be considered as of third importance. 

The following is the classification based primarily upon 
origin and secondarily upon form : J — 



I. Eruptive 
II. Mechanical 



III. Chemical 



J (a) Disseminated. 
\ (b) Massive. 

(Sedimentary). 

(a) Precipitated. 

(b) True veins 

(c) Replacement. 

(d) Impregnation. 

(e) Concretionary. 
(/) Segregated. 

(g) Contact 



i. Chamber deposits. 

ii. Gash veins, 

iii. Fissure veins, 

iv. Ore channels. 



i. By sublimation, 
ii. By concentration. 

I. Eruptive Deposits. — Already the eruptive deposits of 
original disseminated nature have been described, and it has 
been stated that nearly all eruptive rocks contain ores in 

1 This classification might be much more minutely subdivided, bnt this 
seems hardly necessary for our purpose. Various classifications of ore 
deposits will be found in the following works : Report of Michigan State 
Board of Geological Survey for 1891-92, p. 144 ; Davies, Metalliferous Min- 
erals and Mining, p. 8 ; Phillips, Ore Deposits, p. 3 ; Whitney, Metallic 
Wealth of the United States, p. 34 ; Newberry, School of Mines Quarterly, 
1880, p. 337 ; Raymond, Mining Statistics for 1870, p. 448 ; Pumpelly, John- 
son's Cyclopedia, 1886, VI., p. 22; Geikie, Text-Book of Geology, p. 589 ; 
Le Conte, American Journal of Science, Vol. XXVI., 1883, p. 17 ; Le Conte, 
Elements of Geology, p. 234 ; Emmons, IT. S. Geol. Survey, Monograph, 
XII., p. 368. Classifications of ore deposits are also found in the German 
text-books of Von Cotta, Grimm, Serlo-Lottner, and Von Groddeck. Since 
this went to press a comparison of the various classifications has been 
published in Kemp's valuable treatise on Ore Deposits of the United States, 
pp. 42-65. This author also presents a classification of his own. 



ORIGIN OF ORE DEPOSITS. 81 

greater or less quantities, though not in sufficient abundance 
to be classed as ore deposits without the intervention of 
some agent of concentration. The other subdivision of 
eruptive deposits, the massive, is almost equally unimpor- 
tant. There is no deposit of ore, known to be of eruptive 
origin, which is at present worked, although the deposit of 
native iron in Greenland, occurring in a basalt, is sufficiently 
rich to pay for extraction, provided its location was more 
favourable. This group may therefore be dismissed, its only 
importance being as a source of metalliferous substances for 
concentration under other conditions. 

II. Mechanical Deposits (Figs. 16 and 17). — When a 
rock containing metals is disintegrated by weathering, the 
products of disintegration go off, partly in solution, partly 
as mechanical sediment. It is chiefly in this manner that 
disseminated deposits become introduced into sedimentary 
rocks. Usually metalliferous minerals are easily decom- 
posed, and frequently, as a result of their decomposition, 
soluble salts are produced, or a very fine powder of hydrated 
and oxidized ore, which may be disseminated through fine- 
grained rocks. When, however, the mineral is compara- 
tively indestructible, as in the case of gold, platinum, and 
oxide of tin, it outlasts many of the other minerals of the 
disintegrating rock, and may become concentrated. Where 
the chemical durability is combined with mechanical strength, 
as in gold, which is not brittle and not easily worn down, 
this concentration is favoured; but under ordinary circum- 
stances this would hardly attain economic importance, were 
it not for the high specific gravity of some of this class of 
minerals. Gold, for instance, is disseminated through cer- 
tain rocks, but in such small quantities that by their mere 



82 ECONOMIC GEOLOGY OE THE UNITED STATES. 

decay, without the assorting action of water, it would hardly 
be accumulated. Given, however, a rapid stream, the lighter 
minerals are carried off, while the heavy gold accumulates 
in pockets where the currents are less rapid. Such deposits 
are of the mechanical type, including not only the accumu- 
lations in stream gravels, but also those in talus deposits and 
those which more rarely accumulate along shore lines, where 
conditions are favourable. When the three metals, tin, plati- 
num, and gtfld, are excluded, this class of metalliferous 
deposits becomes unimportant. 

III. Chemical Deposits. — This group of ore deposits in- 
cludes all which come into their place by chemical action, 
and in it are included the vast majority of metalliferous 
deposits. There are a number of ways in which this form 
of mineral concentration is brought about, all of which, with 
the exception of some of the contact deposits, are caused by 
the intervention of water. 

(a) Precipitated Deposits. — Precipitated deposits, in the 
sense used here, include those which are formed by precipi- 
tation from solution, at the surface, when the liquid which 
carries the minerals loses its power to hold them, either as 
the result of the loss of some of its properties, or by the 
accession of some substance which causes a precipitation. 
The simplest illustration of this class of mineral deposits is 
that of bog iron ore, where water which has carried in solu- 
tion the hydrated sesquioxide of iron, obtained from the 
soil or the rocks, is, in the presence of certain vegetable 
acids, unable to maintain the solution, and the ore is precipi- 
tated frequently in a bog. Moderately extensive beds of 
impure iron are thus sometimes formed, and, being buried 
beneath other strata, become truly bedded deposits (Fig. 5). 



ORIGIN OF OEE DEPOSITS. 



83 



Practically the same class of deposit is formed about an iron 
spring, where the iron-bearing water, rising from the earth 
to the surface, loses some of its gases, and hence some of its 
power as a solvent, and is forced to deposit the iron about 
the spring. Applied to non-metalliferous minerals, the pro- 
cess finds illustration in the stalactites of caverns and the 
siliceous sinter about hot springs. In some cases true veins 
illustrate very nearly the same principle ; but probably other 




Fig. 5. — Bedded deposit of iron (a). 

causes enter, and this group is so distinct in form and char- 
acter that they will not be classed here. 

(6) True Veins. — The term true veins is here given to 
those occupying pre-existing cavities where the mineral 
deposits have been placed by the agency of water. That 
percolating water is constantly active in its effort to fill cav- 
ities is shown by the study of fossils, such as Ammonites 
(shells allied to the chambered Nautilus of the present), 
where the chambers are filled with calcite, or silica, or even 
ores. The same is true of the gas cavities in lava flows, 
where geodes or amygdules are formed from the wall of the 
cavity toward the centre. The term true vein applied to 
such deposits is perhaps a trifle irregular, although there is 
no genetic difference between deposits from water in small 



84 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



cavities and those in the type of the true veins, — the exten- 
sive fissure veins. 

i. Chamber Deposits (Figs. 21 and 23), or cave deposits, 
are closely allied to these small cavity deposits. Here the 
source of the mineral is usually local, often from the same 
stratum in which it is accumulated. The process is allied to 
segregation, excepting that a cavity furnishes a place for 
accumulation. On the other hand, some chamber deposits 
are so nearly allied to precipitated deposits that they might 
very well be classed in that group. Stalactites furnish 
instances of this form of accumulation, and in some of the 
chamber deposits true stalactites of ore are formed. 

ii. Crash Veins (Figs. 20 and 21) are comparatively rare 
and very local. The rock is cracked and spread apart, 
forming a local fissure, usually confined to one layer or 
stratum; and in these, as in the chamber deposits, the 

supply of ore is evidently 
local. Both chamber de- 
posits and gash veins are 
illustrated in the lead-zinc 
mines of the Mississippi 
Valley. 

iii. Fissure Veins. — The 
type of fissure veins (Fig. 6) 
is perhaps the most common 
of all veins. The distin- 
guishing feature of such accumulations is that they occur in 
a fault or fissure in the earth. Such veins are frequently of 
great extent both vertically and horizontally, but their width 
is relatively small. Usually the bounding walls are distinct, 
although sometimes they are crushed and penetrated by 




Fig. 6. — Fault plane occupied by a vein 
— a true fissure vein. 



ORIGIN OF ORE DEPOSITS. 85 

the vein-forming mineral ; or the solid wall may be impreg- 
nated by the ore (as described below), either of which con- 
ditions tends to make the bounding wall indistinct. There is 
in these veins evidence enough, in many cases, to prove that 
the mineral deposits came from water which passed through 
the vein, apparently from below upwards. This evidence 
is present in the banding of the minerals forming the vein, 
the same minerals being found in succession on each side of 
the centre. That is, if quartz is found next to the country 
rock on one side, this mineral is found in the same position on 
the opposite side ; and if copper pyrite is found next to this 
on one side, it is present in the same position on the opposite 
side. 1 This banding is often very complex, and at times the 
cavity is completely filled, while in other veins the process of 
deposition was interrupted before the filling was complete. 

It is possible to explain this process satisfactorily by 
assuming that heated water, either acidic or alkaline, was 
escaping from the heated parts of the earth's crust toward 
the cooler surface portions, and that as the water rose it lost 
in heat, and perhaps also in its acid or alkaline contents, and 
hence in its power as a solvent. Deposition from the super- 
saturated solution might then be made necessary. Under 
uniform conditions of temperature and foreign contents there 
would be a uniformity of deposit at a given place ; and in 
proceeding from below upwards there would be a progres- 
sive change in the character or amount of deposit. A slight 
change, either a loss or an accession of heat or of contained 
substances, would bring about a change in deposit at differ- 
ent parts of the vein. These changes might occur vertically 
at the same time as the water ascended and lost heat, or 

1 See Fig. 12, p. 98. 



86 ECONOMIC GEOLOGY OF THE UNITED STATES. 

horizontally at different times as the conditions at a given 
point changed. It is highly probable that some of the hot 
springs which are found in various parts of the country are 
the points of escape of metalliferous-bearing waters which are 
at present engaged in the formation of mineral veins. 1 

There are certain peculiarities, found at times, not only in 
fissure veins, but in other mineral deposits as well, which 
call for a modification of this general statement. The verti- 
cal variations in the character of the ore are not always those 
which can be accounted for by the mere vertical change in the 
character of the ore-bearing solution, but in some cases these 
changes are apparently due to the influence of the surround- 
ing rock. This has led to the theory that mineral veins are, 
in some cases, either supplied with mineral, partly or wholly 
from the enclosing rock, by lateral secretion, 2 or that by 
some electrical influence the character of the ore deposit is 
modified by the presence of some particular rock. It seems 
probable that both of these processes act, but that the chief 
cause of these mineral veins is the ascension of ore-bearing 
water from below and the deposition of the mineral without 
the intervention of these outside agents. 

iv. Ore Channels is a term given to those planes of weak- 
ness which exist between two series of rocks, either between 
two eruptive rocks, or an eruptive and sedimentary or meta- 
morphic rock, or along the unconformable contact of two 

1 A definite instance of this process is found at the Sulphur Bank Quick- 
silver Mine in California (see chapter on Mercury). 

2 Sandberger's experiments on the metalliferous contents of common rocks 
(described above, p. 73) have given much support to the theory of lateral 
secretion. These experiments have proved that these sources may supply ore, 
and have made it probable that they sometimes do ; but the proofs are not 
sufficient to warrant the widespread application given the theory by some. 



ORIGIN OF ORE DEPOSITS. 



87 



series of sedimentary strata. These planes furnish channel- 
ways for the comparatively easy escape of subterranean 
waters. The remarks made in speaking of the fissure veins 
hold almost equally for these, excepting that the water is 
less liable to come from great depths, the channel-way is less 
distinct, and the influences which bring about deposit are 
more apt to resemble those of the more superficial deposits, 
such as those in chambers. It must, however, be borne in 
mind that even at shallow depths the earth may be highly 
heated by the intrusion of igneous rocks, and hence a supply 
of heat be furnished to subterranean water channels of com- 
paratively superficial origin. 

(<?) Replacement Deposits. — Certain minerals seem par- 
ticularly liable to solution and replacement by a gradual 




Fig. 7. — Bed of limestone, (a) being replaced by iron, particularly in the synclinal 

troughs, b, b, b. 

molecular transfer, after the manner of petrifaction of wood. 
Under the proper conditions, this process may take place in 
any mineral ; but the mineral calcite seems particularly sus- 
ceptible to the change. In the rocks, fossils are thus re- 
placed by a great variety of minerals (silica, iron, copper, 
and many others), one molecule being dissolved by the per- 
colating water, while another is put in its place, until the 
transfer is either complete, or is in some way interrupted. 
By this process of replacement entire beds of limestone are 
sometimes dissolved away, and one of the oxides of iron put 
in their place (Figs. 7 and 15). Other minerals are acted 



88 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



upon in the same way, and pseudomorphs — that is, a mineral 
of one kind with the form of another- — are not uncommon 
in nature. 

(cL) Impregnation Deposits 
(Fig. 8). — During the forma- 
tion of fissure veins, and indeed 
of other veins as well, it fre- 
quently happens that the ore- 
bearing solutions enter the vein 
walls and impregnate them with 
metalliferous deposits. These 
are at times replacements of 
pre-existing minerals, and at 
times the result of an accumula- 
tion of the foreign ore between 
the minerals of the country 
rock. Impregnation deposits, 
therefore, even in the same 
vein, may be of several kinds of 
origin : they may be concretion- 
ary, or replacement, and their 
source may be from the solu- 
tions which are filling the veins, 
or perhaps they may even be 
the result of a lateral secretion 
from the country rock toward 
the vein. They do not form 
important deposits by them- 
selves, but are usually a leaner 

Fig. 8. -Impregnation of tin ore at t of ft tme minera l vein . 

East Hull Lovell in Cornwall, a, a, L 
leader or divider. (After Phillips.) A form of mineral deposit 




ORIGIN OF ORE DEPOSITS. 89 

known as Stock werk possibly belongs here. It is found in 
the Cornwall district, and is typically a series of small rami- 
fying veins and irregular bunches of ore, sometimes connected 
with fissure veins, but very frequently separate. 

(<?) Concretionary Deposits (Fig. 9). — It is easy to under- 
stand how deposits of ore accumulate in gravels, and in what 
manner minerals are chemically precipitated. The process 
of replacement is analogous to well-known phenomena, and 
the formation of mineral deposits in pre-existing cavities pre- 
sents no inexplicable phenomena, or, at least, we are able to 
form a conception of their method of origin; but the two 




JUT' 

Concretions in strata, a, a, iron-stone concretions in shale; c, flint con- 
cretions in limestone. 

groups of deposits included under the headings concretionary 
and segregated are much less easily understood. 

A study of the chalk beds of England shows that there 
are nodules and layers of flint which have been formed by 
the accumulation of silica, originally disseminated through 
the chalk, but now gathered together about a common 
centre, or along a common line or plane, and a similar condi- 
tion exists in many beds of limestone. In slates, originally 
deposits of clay or fine-grained fragments of disintegrated 
rocks, it is not uncommon to find crystals, and bunches of 
crystals, of iron pyrite, which have been formed by the 
gathering together of the sulphide of iron from the surround- 
ing dense rock,, and its concentration where there was no 
pre-existing cavity. The iron-bearing clay rocks frequently 



90 ECONOMIC GEOLOGY OF THE UNITED STATES. 

contain concretions of limonite, or of hematite of the same 
origin. How does this happen? By what force are particles 
of like nature drawn together from a given area to a grow- 
ing concretion, forming a space for itself often in a compact 
rock ? These are questions which the author has never seen 
explained in a satisfactory manner. 

(/) Segregated Deposits (Fig. 10). — If it is difficult to 
answer these questions in the case of concretions, it is still 




a 

Fig. 10. — Segregation of iron (a) in schistose strata. 

more difficult to answer them when asked about the forma- 
tion of the much more extensive segregated deposits. These 
occur most commonly as veins, often of considerable extent, 
though usually small and non-continuous, one beginning 
and fraying out, while another starts in the same general 
direction as if it were a non-continuous extension of the 
first. Sometimes they seem to have started in small cavities, 
or along planes of weakness; but with even greater fre- 



ORIGIN OF ORE DEPOSITS. 91 

quency, the entire space which they occupy seems to have 
been formed by the growing accumulation. They are gener- 
ally parallel with the bedding or structural planes of the rock. 

Segregated deposits occur most commonly in metamorphic 
rocks and, indeed, much of the metamorphism of strata 
seems to consist in segregation. Starting, let us say, with a 
clay rock of complex composition, the resultant of the decay 
of feldspar and hornblende, pressure and heat begin to act, 
and this, with the aid of the enclosed water, commences an 
alteration of the rock. The old decayed minerals commence 
to assume a more permanent and definite chemical com- 
position and, indeed, to revert to their original composition. 
New feldspars and hornblendes and iron oxides are formed, 
and these different minerals by metamorphism tend, in many 
cases, to arrange themselves in bands which are at right 
angles to the direction of pressure. Actual melting does 
not take place, the new minerals are slowly evolved, and, as 
they develop minerals of the same kind, tend to form in 
clusters ; in this case, in linear clusters. Thus, bands of 
hornblende, of iron, and of feldspar are formed, rarely 
strictly pure, but tending toward purity. 

How far segregation accounts for ores it is difficult to say. 
Some ascribe to this process a very great importance, while 
others are inclined to* consider it of minor importance ; and 
it is true that the evidence of segregation is often obscure. 
Nevertheless it is a cause, and an important cause, par- 
ticularly in metamorphic rocks. In sedimentary strata, it 
rarely expresses itself in any other form than that of con- 
cretion, and in unmetamorphosed igneous rocks the tendency 
to segregate is shown in the banding of minerals, and in the 
spherulitic concretions in lavas. 



92 ECONOMIC GEOLOGY OF THE UNITED STATES. 

When asked what segregation is, one can answer only that 
it is a force which causes like minerals to gather together, 
and is merely another form of concretion. We know that, 
by some form of attraction, molecules of a given substance 
will accumulate to form a mineral crystal, each particle that 
can be drawn to the crystal being added to it. There is 
here certainly some attractive force — " chemical affinity." 
In segregation, perhaps, the same force is at work. Its 
attractive power is strong, for it draws material from con- 
siderable distances ; and, once started, its force seems to be 
increased until a neighbouring area is leached of all the 
desired mineral that is in a form admitting of transfer. 
Heated water seems to increase the tendency, and the initial 
presence of cavities appears frequently to give an opportunity 
for a beginning, though by no means is this a necessary 
starting-point. In true mineral veins, the same tendency of 
accumulation is shown under more favourable circumstances 
of supply and opportunity. What the attractive force is 
cannot be told. It is a force, and it acts in the above man- 
ner, and we therefore have a name and a definition, which is 
perhaps as satisfactory as if we attempted to assign it to 
a place among some of the slightly understood forces of 
nature. It might be called an electro-chemical process, as 
indeed it has been, and, in spite of denials, this seems still 
a not unreasonable explanation. 

(#) Contact Deposits (Fig. 11). — By the contact of igne- 
ous rocks, highly heated and molten, the surrounding layers 
may be markedly modified, particularly when large masses 
or bosses of igneous rocks are intruded at considerable 
depths. Such masses take many years, probably centuries, 
to cool, and during all this time they are tending to alter the 



OKIGIN OF ORE DEPOSITS. 93 

surrounding rocks, not alone by their heat, but chiefly by the 
aid of the aqueous vapour or superheated water, which is 
present in abundance in all lavas. A zone of contact meta- 
morphism is thus produced, in which to a distance of many 
yards the surrounding rocks are often altered past recog- 
nition, by the development of new minerals both from the 
material in the country rock and from the gases furnished 
by the lava. 

In such positions mineral deposits formed in several dif- 
ferent ways are not uncommon. By sublimation, as in the 




Fig. 11. — Contact deposits (a), between and in shale (b), and diabase (c). 

case of mercury and sulphur, mineral deposits may be 
formed at or near the contact as the result of condensation, 
from the gaseous condition of substances emanating from 
the igneous rock. More commonly the presence of the 
lava serves to concentrate minerals along the contact, partly 
from the igneous, partly from the cold enclosing rock, by a 
process of segregation. All deposits along the contact of 
igneous rocks must not, however, be considered as contact 
deposits ; for, by a subsequent process of segregation or con- 
centration, mineral veins may be formed along these planes 
of weakness by the solution of the ore contained in the 
igneous or in the country rock and its deposition here. This 



94 ECONOMIC GEOLOGY OF THE UNITED STATES. 

is the origin of a great many of the apparent contact 
deposits ; but, nevertheless, true contact veins, both of con- 
centration and sublimation origin, actually exist. 

Distribution of Ore Deposits. — It will be noticed in study- 
ing the distribution of ore deposits in any country that they 
are more common in certain parts of the region than in 
others, and this is the direct result of cause and effect. 
Omitting the mechanical deposits which may occur in any 
place where the supply of ore is sufficient and the condi- 
tions of weathering and deposition favourable, the precipitated 
deposits which may also occur anywhere, segregated and re- 
placement veins which are typical of metamorphic or the 
older sedimentary rocks, and the only important groups of 
mineral deposits remaining are the true and contact veins 
which include by far the greater number of mineral deposits, 
if iron, manganese, and stream-gold are excluded. 

These two groups of metalliferous veins are associated in 
origin with either cavities or heat, or both combined. Geo- 
graphically they are associated most commonly with moun- 
tains, and usually with mountains of recent formation. The 
reason is apparent, for in such places there are numerous 
fractures and fault planes, and abundant volcanic and intru- 
sive igneous rocks, — in fact, all the conditions necessary for 
the formation of such deposits. Moreover, in high moun- 
tains erosion has penetrated to considerable depths, and 
hence has revealed to us more of the hidden stores of the 
earth's crust. 

Geologically, in this country the mineral wealth is chiefly 
stored in the less ancient rocks ; that is, in post-Archean 
series, and in many cases in post-Palseozoic strata. This is 
due largely to the fact that these rocks form the greater part 



ORIGIN OF ORE DEPOSITS. 95 

of the recent mountains of the Cordilleras. One might con- 
sider it remarkable that the older strata, which have for a 
longer time been exposed to the action of subterranean water 
and other agents of change should be comparatively so unim- 
portant as mineral producers. There seem to be at least two 
probable causes for this. In the first place, the lower rocks 
being buried beneath a great thickness of overlying strata, 
when subjected to mountain-forming forces tend to fold 
rather than to break, while the less compressed layers nearer 
the surface become more fractured. Fewer cavities, there- 
fore, exist in these older rocks. Besides this these deeply 
buried strata are subjected for long periods of time to a 
leaching of percolating waters which escape toward the 
surface and deposit their dissolved mineral in the cavities of 
the overlying strata. They are robbed of their mineral con- 
tents for the benefit of the overlying layers. If this be true, 
then in older mountains, such as those of New England, 
there may have formerly existed mineral deposits which have 
since been destroyed by erosion. The discrepancy between 
the Appalachians and Cordilleras is also, as has already been 
stated, due to the conditions prevailing during their formation. 
Thus the Appalachians seem to have been formed more by 
folding and less by faulting than the Rockies ; and, also, the 
former were practically without volcanic activity, whereas 
in the Cordilleras volcanic conditions were marvellously 
developed. These differences seem sufficient to account for 
the marked difference in distribution of ore deposits in this 
and in other countries, showing the intimate relation which 
exists between geologic conditions and mineral wealth. 



CHAPTER V. 

MINING TERMS AND METHODS. 1 

Mining Terms. — A mineral may be defined as an inorganic 
substance having theoretically a definite chemical composi- 
tion and frequently a definite geometric form. It is usually 
a combination of elements, though sometimes a single 
element, as gold, sulphur, etc. Miners use the term mineral 
as a synonym of ore, which is, according to the economic 
standpoint, a metal, usually mineralized, occurring in sufficient 
quantities and in such combinations as to be economically 
valuable. 

Elements are of two kinds, metals and metalloids, though 
some have properties common to both groups, and the dis- 
tinction is much less sharp than Avas at one time supposed, 
before all the elements were carefully studied. The typical 
metal has certain definite characteristics, being basic rather 
than acid in its properties, having a considerable specific 
gravity and a metallic lustre. In the arts the metals serve 
different purposes, depending upon their physical characters, 
some being bright, beautiful, and not easily tarnished; some 

1 That part of this chapter which refers to mining methods is necessarily 
brief and generalized, and refers only to the more important processes. 
There are text-books which give in detail information upon this subject; 
but the only way in which such knowledge is properly obtained is by a study 
of the mines themselves. A good short account of mining terms and 
methods will be found in the last part of Davies, Metalliferous Minerals and 
Mining, and other treatises are referred to in the list of books of reference 
at the close of this work. 

96 



MINING TERMS AND METHODS. 97 

having hardness, or ductility, or malleability, or a low or high 
melting-point, etc. The metals which we know best, such as 
gold, silver, iron, copper, etc., are, with the exception of iron, 
comparatively rare, while the most common metals, such 
as aluminum, calcium, magnesium, etc., are comparatively 
rare in the arts. Of the metalloids, oxygen, silicon, and 
carbon are the most common. 

As has already been stated, these elements combine in 
different proportions to produce minerals, some of which are 
ores. In the mineral vein there are not only ores, but also 
very frequently foreign minerals which make the veinstone 
or gangue, a foreign, mechanical mixture of minerals which 
are of no economic value. Thus, not only are calcite and 
quartz considered to be gangue, but also such metalliferous 
minerals as iron pyrite, which have to be separated from the 
ore by mechanical processes. When minerals combine to 
form a fixed and essential part of the earth's crust, a rock is 
formed, and these may result from crystallization by meta- 
morphism, or from solution, or from a molten condition, or 
they may be produced by the mechanical destruction of 
pre-existing rocks and the accumulation of the fragments. 
Ordinarily the term rock is applied to a solidified accumu- 
lation of minerals, but in reality it should be made to include 
unsolidified deposits as well, since there is every gradation 
between the unsolidified and solidified sometimes in the same 
bed. There is some difference of opinion as to the propriety 
of including veinstones under the term rock ; but it seems 
better to consider them as minerals, although miners some- 
times speak of the veinstone as vein-rock. 

A vein, as well as a rock, is said to outcrop where it 
appears at the surface in a natural exposure, — or where 



98 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



it crops out. In California the outcrop of a vein is fre- 
quently called a ledge, since the outcrops for which the 
prospectors of that region were most anxiously looking, 
being of hard quartz, formed a ledge. For the same reason, 
the term reef is used in Australia, this name being suggested, 
no doubt, by the resemblance to the coral reefs of that 
region, which project above the ocean. Instead of a ledge- 




Fig. 12. — Section of mineral vein showing ribbon or banded structure and sym- 
metrical disposition of the various mineral bands. A, country rock; B, 
fluccan ; C, comb structure ; 1, iron pyrite ; 2, calcite ; 3, quartz ; 4, mag- 
netite; 5, barite; 6, chalcopyrite ; 7, galena; 8, quartz. 

like outcrop, it is more common for many mineral veins to 
be marked by a depression caused by the weakness of the ore 
or the gangue, or both. In such cases the ore is often hidden 
and discovered by accident, though its position may be indi- 
cated by loose boulders, or by a stain or rust characteristic of 
the metal. The Cornish miner calls this gossan, while in 
France and Germany it is called the iron hat, 1 because of 
the characteristic iron stain. For a vein the term lode is some- 
times used meaning a deposit which the miners are following 
1 Chapeau de fer and eisener Hut. 



MINING TERMS AND METHODS. 



99 



in the expectation of finding something valuable, — the deposit 
which is leading them, hence sometimes called a lead. 

In the vein, one of the most striking features, provided it 
is a true fissure vein, is the banded structure (Fig. 12), due 
to the regular arrangement of the various layers on either 
side of the centre. At times 
the vein is completely filled ; 
but it is frequently the case 
that it is only partly filled, and 
the projecting points of the 
crystals last formed produce a 
serrated surface known as the 
comb structure (Fig. 12) . Frag- 
ments of foreign rock, included 
in the vein, are called horses 
or riders (Fig. 13), and these 
are usually broken from the 
neighbouring or enclosing 
country rock or country (Fig. 
12 and 13), though sometimes 
they are included between 
two veins. The country rock 
is sometimes sharply defined, forming the vein wall; and 
since nearly all veins are more or less inclined, the two 
walls are called respectively hanging and foot walls (Fig. 
14), according as they are overhead or beneath the feet. 
Between the vein and the country rock there is fre- 
quently a clayey substance, clay selvage, flucean, 1 or gouge 

1 This, like many of our mining terms, is a Cornish name, for from this 
district we have obtained not only many of our mining methods, but also 
much of our mining nomenclature. 




Fig. 13. — Vein of blende and galena 
(A) in a gangue of quartz and calcite 
(B), including horses (H) of the 
country rock (C). (From Davies.) 



L.oFC. 



100 ECONOMIC GEOLOGY OF THE UNITED STATES. 

(Fig. 12), which is sometimes the result of decay, sometimes 
of faulting and crushing by a movement between the vein 
and wall. It is of value in mining, because it is easily 
removed, it enlarges the vein, gives a smooth firm wall, and 
is, moreover, a good sign, since it is more common in fissure 
veins than elsewhere, and such veins are more liable to be 
permanent. By this subsequent movement in the vein the 
walls, and even the different parts of the vein, are often 
polished and grooved or slickensided. A careful study of 
slickensides frequently shows where to look for the continua- 
tion of a vein which has been lost by being moved out of 
position by a cross-fault. During the formation of the 
fissure in which the vein is located the country rock is some- 
times crushed and brecciated, and during the formation of 
the vein these fragments may be cemented by either gangue 
or ore. Subsequent movements may again open the vein, 
either causing a new fissure or crushing the vein-rock to a 
breccia. 

The horizontal direction of the vein is called its strike, or 
by miners very frequently the run or course. Veins rarely 
extend vertically into the ground, but generally dip or hade 
at a greater or less angle. In geology, the dip is measured 
in degrees from the horizontal ; but in some mining districts 
it is measured from the vertical, the one being then the com- 
plement of the other. In some of the English districts this 
angle is called the underlie. Besides the dip there is some- 
times present a pitch, a term which refers to a dip of the 
entire vein or pocket in the direction of the strike. The 
relation of the ore to the surrounding rock, together with 
the strike, dip, and position of the vein, is shown by means 
of various plans and sections. A geological map gives in 



MINING TERMS AND METHODS. 101 

horizontal plan the various rocks which enclose the vein; 
and if it is desired to show the horizontal appearance of the 
vein, or of its tunnels at different depths, ground plans are 
made to show these features. Where it is desired to show 
the linear extent of the vein and of its tunnels, and the 
position of the shafts, a longitudinal section or plan is made 
parallel with the plane of the vein. A cross-section is one 
made at right angles to the strike of the vein, and shows its 
dip, the position of the enclosing walls, and also the position 
of the shafts and tunnels in the line of the section. The 
geological map and the cross-section show most clearly the 
geological structure, but the ground plan and longitudinal 
section are the most valuable in showing the position and 
number of the tunnels. 

Variation in Veins. — During the process of mining there are 
often found to be variations in the character or position of the 
ore. The vein varies in width, swelling and pinching , sometimes 
by original irregularities, at times as the result of an actual 
squeezing in of certain parts of the vein, forming alternate 
pinches and swells. The walls roll, the miners say, since 
they seem to form waves. Actual faulting may cut off the 
vein, and the miner finds the ore ending abruptly against 
a wall of barren rock. These faults are sometimes of small 
extent, in which case the vein is readily found again ; but in 
some cases valuable veins are completely lost. In a given 
district veins have a prevailingly uniform direction, fre- 
quently parallel to the direction of the strike of the rocks 
or of the mountain range. Yet, on the other hand, they may 
be very irregular in direction, and in the same district two 
or more sets of veins may exist. In such cases the veins of 
one set are usually richer than those of another, and they 



102 ECONOMIC GEOLOGY OF THE UNITED STATES. 

may be widely different in character, one set being perhaps 
barren of ore. These veins frequently intersect, the older 
being crossed by the younger, and being displaced by the 
disturbance which formed the vein cavity. A great variety 
of confusing conditions are encountered by miners in con- 
sequence of these intersections of veins; but a careful study 
of the geology of the district will usually aid in the solution 
of the problems thus presented. On the other hand, veins 
are frequently lost by becoming gradually more and more 
barren, or sometimes by branching at either end, and thus 
becoming smaller and more difficult to work, and in these 
cases the ore is usually permanently lost. From the main 
vein branch-veins are frequently sent off, and these are called 
droppers or feeders, the latter name being given because they 
are supposed to furnish the vein material, though in reality 
these offshoots diminish the quantity of mineral in the vein. 

The ore often varies both in quantity and quality in 
different parts of the same vein. This variation may occur 
even in the same enclosing walls, or it may at times be 
dependent upon a change in the character of the country rock 
showing the influence of the enclosing rocks upon the vein 
material. The variation may amount to a complete change 
in the kind of ore as in the Przibram district of Bohemia, 
and in Cornwall, where the influence of the rock is very 
marked, the ore sometimes changing from copper to tin. 
Change in the character of the ore in a vein is, however, 
most commonly the result of an alteration due to the effect 
of weathering. Below a certain line in the earth there is 
permanent water, the rocks being saturated. This water line 
varies greatly in position according to the climate, being in 
some parts of the arid regions many hundred feet beneath 



• . MINING TERMS AND METHODS. 103 

the surface. Above this line the minerals are subjected to 
conditions of alternation from dry to moist, and conse- 
quently if they are not permanent combinations, to changes 
in character. Most ores are comparatively unstable, and 
under these conditions are altered in composition. Thus 
galena, the sulphide of lead, becomes altered above the 
water line to the sulphate anglesite, and many sulphides 
become carbonates, or oxides, usually of hydrous varieties. 
Moreover, by the solvent power of the percolating water 
metallic salts may be dissolved and carried away leaving the 
ore above the water line more porous. The effect which 
these alterations have upon the richness of the ore is very 
different under different conditions. Thus the native gold 
of California is found enclosed in iron pyrite in quartz rock, 
but by weathering the iron pyrite is removed, and it was 
supposed in the early days of the mining industry of Cali- 
fornia, that the gold became less abundant as the depth of 
the mine increased ; but with the present methods the gold 
•is easily extracted from the pyrite. On the other hand, 
instead of carrying away the gangue in solution, the perco- 
lating water may destroy the ore and thus make the vein 
above the water line less rich. This, however, is often more 
than compensated for by the increased difficulty of mining 
or reducing the unweathered ore from below the water line. 
For different ores and gangues and for different climates the 
conditions of weathering vary so that no general statement 
can be made, but each district may have a peculiarity of 
its own. 

Mining Methods. — In order to obtain a metal, there are 
usually four processes which must be used, — mining, dressing, 
concentration, and reduction. The first three processes are 



104 ECONOMIC GEOLOGY OF THE UNITED STATES. 

mechanical, the fourth depends upon chemical reactions. 
In mining, the first step is naturally to find the vein, and 
for this, very different methods are in use in different parts 
of the world and for different kinds of ore. The Cornish 
miners speak of shoding, shodes being fragments of veins 
increasing in size as their source is approached ; and shoding 
consists in tracing these fragments to their source. American 
miners have invented for this process of ore-finding the term 
prospecting, a prospector being one who is in search of a 
prospect upon which to base future work. At the time of 
the development of the gold fields of California in the years 
succeeding 1848, a horde of people of all classes turned 
prospectors, and even at present there are thousands of such 
people in the Cordilleran region, now, as then, for the most 
part barely eking out a living, though ever in hope of 
finding some prospect which shall yield them a fortune, 
as some of their numbers have already done, in some cases 
several times. 

The original prospector confined his attention to the 
streams, washing the gravels here and there, in search of 
placer deposits. When this field became fully occupied and 
less paying, the attention of many of the prospectors was 
turned to other deposits, and these men have, in many cases, 
developed a wonderful degree of skill in the detection of 
ore deposits, — a skill which the trained mining engineer 
may well covet. Their methods consist chiefly in the appli- 
cation of a wide experience, by which they are able to tell 
where not to look for ore, and what is the surface appearance 
of various common metalliferous deposits. The characteristic 
rust of a metal, as the green of copper, or the yellow of lead, 
the crumbly, disintegrated appearance of the outcrop of an 






MINING TERMS AND METHODS. 105 

ore, and the appearance of characteristic vein minerals, all 
serve as guides. More scientific methods, which are some- 
times possible, the prospector does not usually possess ; but 
the vast majority of mines in the west have been discovered 
either by pure chance or by the application of these methods. 

Having found a surface indication of ore, the next step 
is to develojj in order to see if there is a "show," and if so, 
to give the property a market value. If the outcrop is not 
already fully revealed, enough work is done to see in which 
direction the vein strikes ; and then, in order to test its 
extent, cross-cuts are made at right angles to the strike, the 
earth being removed down to the bed rock until the vein is 
encountered, and this is continued at intervals of a few 
yards until the miner is convinced of the probable direction 
and extent of the vein. Since most of the newly discovered 
ore deposits in the west are situated upon government land, 
the miner must then locate his claim at a government land 
office, and then, within a specified time, do a sufficient 
amount of work to become the absolute owner of the land. 
If the deposit is of much value, it is usually not long before 
others have located claims near by, and the whole region 
is crossed by these claims, often in such inextricable con- 
fusion that long-continued litigation results, and the profits 
of the mining operations are diverted. 

Subsequent development depends largely upon the local 
conditions, the character and position of the ore primarily, 
as well as the probable future of the mine. The immediate 
purposes, or even, in some cases, the permanent development, 
of the mine may be best served by opening the deposit as 
a pit or as a quarry, although the most common method is 
to open a mine, or a series of shafts and tunnels. In the 



106 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



serious development of a mine, the most important thing 
to be taken into consideration is drainage, and this gives 
to miners more trouble than any other single need. The 
simplest possible condition is to commence the mine upon a 




Fig. 14. — Diagram showing usual method of exploiting a vein. V, vein or lode; 
H, hanging wall ; F, foot wall ; D, intrusive diabase ; Sh, shale ; SS, sand- 
stone; Cg, conglomerate; S, shaft; A, adit level; C, C, C, cross-cuts. 

valley side, and drain it into the valley, as the work of 
development progresses, using the lowest tunnel for a 
drainage way. Where this is impossible, it is frequently 
found economical to extend a horizontal shaft, tunnel, drive, 



MINING TERMS AND METHODS. 107 

or adit level (Fig. 14), as it is variously called, to some 
neighbouring valley, and this is often done at an immense 
expense, the expenditure of years in construction, and the 
formation of a tunnel sometimes several miles in extent. 1 
When this is impossible or impracticable, pumping is 
resorted to, but this is an extremely expensive process in 
deep mines. 

When the vein is vertical, a shaft may be sunk in the vein 
and the material removed made to pay the expense of con- 
struction ; but most veins are inclined, and then one of two 
things is possible, — either to work on the incline and hoist 
the ore on inclined tracks, or to construct a vertical shaft 
which shall intersect the vein at a considerable depth and be 
connected with it by a number of short horizontal tunnels ; 
and in well-developed mines this is usually done. The width 
of the shafts and tunnels varies with the amount of work to 
be done. In working along the vein or lode, horizontal 
tunnels or " drifts " are made through which the ore is hauled 
to the shafts, where it is hoisted to the surface. Usually 
there is more than one shaft, often a number, connecting dif- 
ferent levels or drifts, these being used partly for hoisting 
ore, partly for ventilation (" winzes "), which every well- 
developed mine must take into account. From the drifts 
and small shafts the ore is worked or " stoped " out, some- 
times by overhand, sometimes by underhand, stoping ; that 
is, from above or below. In this stoping, secondary drifts 
and partial shafts ("mills") are constructed to facilitate the 
process of ore extraction. 

During the process of mining the lode is completely honey- 

!The Sutro Tunnel of the Comstock Lode in Nevada is 20,489 feet in 
length, and meets the Lode at a depth of 1900 feet. Its cost was $ 2,000,000. 



108 ECONOMIC GEOLOGY OF THE UNITED STATES. 

combed by these various excavations. 1 In old-fashioned or in 
poorly developed modern mines, the excavations are irregular 
and the tunnels rudely constructed, being confessedly tem- 
porary ; and when one part of the mine is worked out, it is 
abandoned to its fate. Where better and more permanent 
methods are used, pillars of ore are left to support the roofs 
of the tunnels, and the shafts and tunnels are carefully tim- 
bered to prevent collapse. For this purpose, not only is 
much valuable ore left behind, but often millions of dollars 
are expended in timbering, particularly in some of the larger 
mines of the Cordilleras, where timber is scarce and difficult 
to obtain. This timber is a danger in one respect, since it is 
liable to be burned and cause a temporary abandonment of 
the mine as well as great expense in retimbering. During 
the development of the Comstock Lode, a novel difficulty 
was encountered which all large mines, extending to great 
depths into the earth, are liable to encounter in time. This 
is intense heat, which, in the Comstock, was encountered at 
a point unusually near the surface, owing, no doubt, to the 
proximity of heated rocks of igneous origin. Floods of hot 
water burst through the walls, and flooded the mine, heating 
the air so that work was well-nigh impossible. It was neces- 
sary to pump cold air into the galleries, and even then slight 
physical exertion was nearly impossible, so that eventually 
the lower tunnels of the mine had to be abandoned. 

Excepting for the general direction of operations, the 
process of mining in itself is purely mechanical. One fun- 
damental principle is followed, — to leave below as much of 

1 In 1880 there were more than one hundred and fifty miles of shafts and 
galleries in the Comstock Lode, and since then these have been somewhat 
increased. 



MINING TERMS AND METHODS. 109 

the gangue as is possible. Hence each miner directs his 
labours so as to avoid barren areas, and, where possible, to 
make them serve as supporting pillars. The ore is drilled, 
blasted, or picked, according to its nature ; and in selecting 
material to be sent to the surface, the fragments are roughly 
assorted in the mine in order to send out of the mine as little 
valueless mineral as need be. For transportation from the 
point of mining to the shaft, various methods are used, such 
as wheelbarrows, horse railroads, cable, gravity, or even, at 
present, electric roads. Having reached the shaft, it is 
hoisted to the surface by a method depending upon the scale 
of operations adopted in the mine, this varying from hand 
power to electricity. 

The mines in Europe are frequently owned and operated 
by the government; but in this country they are in the 
hands of private owners, who usually direct all operations, 
although in some of the western mines a method of working 
known as the tribute system is in operation. Certain parts 
of the vein, and at times the entire mine, are turned over to 
individual miners or groups of miners to develop on shares. 
This method is usually adopted in mines where the amount 
of ore varies greatly, and where rich pockets occur in great 
areas of barren gangue, or in mines which have been aban- 
doned because of the average poverty of the deposit. It is 
probable that the average result of this system is far from 
profitable to the miner, but the element of chance and the 
possible riches which are sometimes won is a sufficient incen- 
tive to many miners to enter into the tribute system. The 
owners risk very little, but this system is usually bad for a 
mine, since the tribute miners generally leave it in a bad 
condition, and not properly timbered or ventilated. 



110 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Concentration of Ores. — When the ore has arrived at the 
surface, the mechanical process is still farther pursued in 
separating the ore from the gangue. This is often done, 
first by breaking the fragments into smaller pieces, generally 
by hand, and then by the separation, also by hand, of the 
very lean ore and gangue from the richer fragments. The 
ore is now in a fairly concentrated condition, but is still in 
combination, mechanically with some of the gangue, and 
chemically with the mineralizer. The methods used for the 
extraction of the metal from these associations are extremely 
varied, depending both upon the character of the ore and 
the development of the mine. A few of the more important 
methods only are briefly described here. 

The first thing to be done in gold-bearing quartz and some 
other ores is to crush the ore so that even the finest particles 
of foreign, mechanically associated mineral may be removed 
by water. This is done by means of the stamp, an apparatus 
so old that the time of its invention is not known. There 
are many kinds of these, the most improved being the 
piston stamps in which a heavy head, weighing in some 
cases a ton, is raised to a height of from twelve to fourteen 
inches and then dropped. In some of the better equipped 
mills not only do the piston stamps work automatically, but 
the ore is fed in the same manner, and one may pass through 
such a mill, where many stamps are at work, without seeing 
any other workmen than the watchmen. 

In the placer gold, platinum, and stream-tin deposits 
nature has performed the duties of the stamp mill in disin- 
tegrating the rock which contained the ores ; and to a cer- 
tain extent, also, the duties of the cencentrator by the 
assorting power of running water. This same principle is 



MINING TERMS AND METHODS. Ill 

made use of in much of the separation of ore from gangue. 
Placer miners separated the heavy gold from the admixture 
of gravel by means of a pan or some similar contrivance, 
simply giving to it a peculiar shaking motion which caused 
the heavy gold to accumulate in the bottom of the pan, 
while the lighter gravel was washed out. The introduction 
of the cradle, an inclined board with riffles, was an advance 
in method which was followed by the sluice, an apparatus in 
which nature's process of concentration is closely imitated. 
This consists of a long box with a rapid slope, built in the 
river valley, into which the gold-bearing gravel is washed 
by streams of water. The gravel rushes down through the 
box, while the heavy gold drags near the bottom and tends 
to collect behind the riffles, or cross-pieces nailed across the 
bottom of the box, just as it does in the streams where the 
current is slackened by a boulder or some other obstacle. 
Two things are necessary : a plentiful supply of water and 
a rapid slope. In some parts of this country, and of other 
countries as well, there are extensive deposits of gold-bearing 
gravel which might be worked by this hydraulic process, if 
water or slope were present. Indeed, in most of the placer 
regions of the west the water supply has presented difficult 
problems, for the solution of which vast sums of money have 
been expended in the construction of canals and water pipes 
for the carriage of water often from one drainage basin to 
another. Even under these circumstances hydraulic mining 
was very successful, and gravel with very little gold was 
worked over with profit. 

In the case of gold-bearing quartz and other ores in which 
the gangue is abundant, the ore is crushed to a pulp or 
" slime," and under different circumstances different methods 



112 ECONOMIC GEOLOGY OF THE UNITED STATES. 

are used for the separation. An ingenious contrivance for 
this purpose is the pointed box, an apparatus consisting of 
several V-shaped boxes of varying size with small apertures 
at the apices. A stream of water passes from one to the 
other, keeping the water in them in circulation, and " slime " 
is fed into the first box, the heavier parts sinking and pass- 
ing out of the opening at the bottom, and the balance being 
carried into the next, where, the current being less strong, 
still more of the heavy particles drop through the aperture. 
Beneath each box there accumulates a pile of material ; pure 
ore beneath the first, pure gangue (" tailings ") beneath the 
last, and beneath the intermediate ones an admixture which 
may pay for further concentration. 

Frame, tye, or huddle, are names given to an inclined 
board upon which crushed ore is fed, together with a current 
of water which carries the lighter material downward, while 
the ore remains near the top, and in the middle there is an 
admixture of ore and gangue which may need to be passed 
again over the frame. A man standing near with a rake 
assists the separation by stirring the slime. Machinery 
works faster, but produces no better results than this rather 
crude method. When jarred by machinery the frame be- 
comes the percussion table, of which there are numerous 
modifications. A constantly moving belt of corrugated rub- 
ber, the vanner, upon which the ore is fed, serves to con- 
centrate it in a similar manner. The jig or jigger, also 
used for this purpose, consists of a box with small holes in 
the bottom. Slime is placed in this, and a jigging motion 
given to the box either by hand or by machinery (piston 
jigger), by which there is a separation of the minerals into 
layers according to specific gravity, the ore seeking the 



MINING TERMS AND METHODS. 113 

bottom. One of these pieces of apparatus, or some modifi- 
cation of it, is used for nearly all ores where the percentage 
or character of the gangue is such as to call for a mechanical 
separation further than that of selection at the mine. Some 
ores of iron and other metals are sufficiently rich when ex- 
tracted to go directly to the smelter without concentration. 
Other ores are in such combinations, as, for instance, with 
some mineral easily disposed of in smelting, or with some 
heavy mineral which cannot be separated by water, that con- 
centration is either not necessary or not possible. 

Reduction of Ores. — For the chemical reduction of ores, 
a few words of the most general nature must suffice. Each 
different ore is treated in a different manner, but in general 
three methods are used: amalgamation, smelting (the dry 
way), and metallurgy (the wet way). The process of amal- 
gamation is used chiefly for the extraction of gold and silver. 
In the case of gold it is used to remove the metal, which 
is mechanically mixed with impurities. Mercury placed in 
the sluices in hydraulic mines, remains behind the riffles and 
greedily seizes all gold which comes within its grasp, forming 
an amalgam with it. Practically the same is done with the 
gold extracted from the quartz rock by crushing and con- 
centration. From the amalgam the mercury is easily driven 
off by heat, and, being collected by condensation, is ready to 
be used over again. For the extraction of gold from its silver 
and other alloys, finer methods are used. The affinity of mer- 
cury for other metals is also made use of as for instance in the 
extraction of silver from certain of its ores. Several processes 
are used, but in general they consist in the use of mercury, 
the crushed ore, and some salt, which are all stirred together, 
in the Mexican mines by driving mules back and forth over 



114 ECONOMIC GEOLOGY OF THE UNITED STATES. 

the ore, but more commonly by machinery. A chemical 
reaction, not very well understood, takes place ; the silver 
is freed from its chemical combination, and enters into an 
amalgam with the mercury, from which, as in the case of 
gold, it is obtained by heat. So important is the use of 
mercury in the extraction of gold and silver that the greater 
part of the supply of this metal is used for that purpose. 

Ores differ very markedly in the strength of the affinity 
which binds the metal and mineralizer together. The chlo- 
ride of silver can be extracted by a very gentle heat, the 
chlorine being driven off and pure silver left. With other 
ores a high heat does the same, and, again, by the use of 
some other mineral as a flux, upon the application of high 
heat the metal is driven from its mineralizer, which enters 
into combination with the flux, while the metal remains free. 
Some ores have to be smelted again and again, and some are 
so difficult to obtain that they are not mined. Every year 
adds to our knowledge of metallurgical processes, or gives 
us some new way of smelting by which it is possible to 
extract the refractory metals more economically. As an 
instance of this the Franklin Furnace zinc mine of New 
Jersey, originally worked for iron, is now kept open chiefly 
for the zinc. Formerly the zinc contained in the oxide 
zincite, the silicate willemite and the oxide of iron and zinc 
franklinite, was considered to be in too refractory combi- 
nation for separation. 

Before smelting some ores it is necessary to either calcine 
them — that is, to allow them to decompose in the air at ordi- 
nary temperatures — or to roast them. This serves to drive 
off a part of the sulphur, or arsenic, or other elements which 
have strong affinities for the metals. The ore is then 



MINING TEEMS AND METHODS. 115 

smelted and the metal obtained. For more detailed state- 
ments concerning the processes of smelting or of metallurgy, 
recourse should be had to some of the treatises upon the 
general subject, or upon special ores or metals. 1 

1 Some of these are referred to in the bibliography at the end of the 
book. 



Part II. 
METALLIFEKOUS DEPOSITS. 



CHAPTER VI. 

IRON. 1 

General Statement. — The ores of iron are, (1) brown hema- 
tite (including all varieties of the hydrated sesquioxide, — 
limonite, gothite, bog ores, etc.) ; (2) red hematite (the 
anhydrous sesquioxide, including specular, micaceous, fossil 
hematite, and other varieties based upon physical character- 
istics) ; (3) magnetite ; and (4) the carbonate (FeC0 3 , in- 
cluding spathic ore, blackband, siderite, etc.). Native iron 
is found in meteorites and in basalt rock, in Greenland, but 
it is not known as an ore. The sulphide, iron pyrite, is 
mined, not for its iron, but for the sulphur which it contains. 

An iron ore, in the present state of the iron industry, must 
occur in a very favourable position as regards market, it must 
be of good quality, in considerable quantity, and favourably 
situated for extraction and smelting. The presence of sul- 
phur or phosphorus in an ore makes it valueless unless the 
quantity is very slight. Iron is now so cheap that, where 
mining operations are difficult, as, for instance, where the 
mine is deep, the vein narrow, gangue abundant, or trans- 
portation difficult, it cannot be mined. There are a suffi- 
cient number of good iron deposits in this country to make 
selection possible, and consequently many of the older mines 
are being abandoned because of the development of these 

1 A very complete account of the iron industry of this country is found 
in Vol. XV., Tenth Census, pp. 1-601. 

119 



120 ECONOMIC GEOLOGY OF THE UNITED STATES. 

more profitable mines. For reasons of this sort, the New 
Jersey region, for instance, which was once an important 
iron-producing section, is becoming abandoned ; and whereas 
only a few years ago there were many score of profitable 
mines in that state, now there are very few. As this ore is 
chiefly magnetite, and some of it of a very high grade, it is 
possible that the use of electricity in the separation of the 
ore, which is now being experimented with, may revolution- 
ize the iron industry of that state. 

The most favourable situation of an iron ore for profitable 
extraction is near good coking coal for smelting and lime- 
stone for a flux, as in the Birmingham district of Alabama ; 
and in such a situation even low-grade ores can be worked 
profitably. Unless this is the case, iron ore cannot be exten- 
sively mined excepting under conditions of great abundance 
and economical methods of transportation, as in the Lake 
Superior district, where thick and remarkably uniform beds 
of good ore occur in such a position that water transporta- 
tion to the market is possible. Where these conditions do 
not exist, iron-mining is feasible only on a small scale for 
the local market. Thus, in the Rocky Mountains, there are 
almost inexhaustible supplies of iron, often of high grade, 
which are at present of no value whatsoever. 

Brown Hematite Ores. — The brown hematite ore (hydrated 
sesquioxide), of which limonite is the most important vari- 
ety, produced, in 1891, 18.9 per cent of the iron ore of the 
country. Of the total output of 14,591,178 tons of iron ore, 
2,757,564 tons were of brown hematite. While in 1880 this 
ore was third in rank of importance, in 1891 it held second 
place in the production of iron. 

Hydrated sesquioxide of iron occurs abundantly in most 



IRON. 121 

soils as a yellow stain, and nearly all percolating water takes 
it into solution. From this it is frequently precipitated in 
bogs, forming bog-iron ore, which is common in New England 
and the northern states generally. Here it was mined in 
the last century and used for iron; but at present, partly 
because of its impurity, partly on account of its local nature, 
this source is not exploited. At present, the greater part of 
the supply of brown hematite comes from the southern states, 
chiefly from Virginia, Alabama, and Georgia, where it occurs 
typically as beds in the nearly horizontal sandstones of recent 
age and in the older slates and limestones; The first mode 
of occurrence is typically illustrated in the iron mines at 
New Birmingham, Cherokee County, Texas, where flat-topped 
hills of erosion, or " buttes," stand up above the surrounding 
country, and in these beds of iron occur capped and under- 
lain by a partially consolidated ferruginous sandstone. The 
ore, which varies in colour from brown to black, and is usu- 
ally granular or semi-compacted, is of the bog-iron variety, 
and is distinctly bedded with the sandstones, having appar- 
ently been precipitated in shallow lakes or lagoons along the 
shore line before the region was elevated in Tertiary times. 
After scraping away the loose or semi-compact sandstone 
covering, the ore is easily removed by picks, and the mine 
worked at a low cost as an open work or pit. There is much 
of this class of ore in eastern Texas and other parts of 
the Tertiary plain, although at present it is very slightly 
developed. 

In northeastern Alabama brown hematite occurs in 
pockets, often of large size, from which it is extracted by 
means of a steam shovel. Pennsylvania is an important 
producer of this ore. In Lehigh County it occurs in slates, 



122 ECONOMIC GEOLOGY OF THE UNITED STATES. 

apparently the result of the decomposition of pyrite, or else of 
concentration by deposition from percolating water. There 
is a more or less continuous band of limonite, often associated 
with manganese, in the limestone belt of early Palaeozoic age 
which extends from Vermont to Alabama. Mines in this 
belt are located at Brandon, Vermont; Richmond, Massa- 
chusetts ; Lehigh County, Pennsylvania ; Shenandoah valley, 
Virginia, and elsewhere. Whether originally precipitated or 
subsequently concentrated, perhaps by replacement, is still 
a disputed point. On the Pacific slope the most important 
iron-producing region is a limonite bed near Portland, 
Oregon. Here, in the Prosser mine, the limonite is found 
in hollows in a basaltic lava flow which has been buried 
beneath a later flow of lava. These hollows seem to have 
been lakes and swamps, as indicated by the association of 
tree trunks and vegetable remains. The supply of iron 
came no doubt from the basalt, from which it was leached 
by water and precipitated as bog ore in the swamps, and 
later buried beneath lava. 

The value of brown hematite, as an ore of iron, consists 
less in its richness or its purity than in the ease with 
which it can be exploited and smelted. Nearly all the 
mines of this mineral are open works, and the ore is soft. 
It is, however, usually local in distribution, and not generally 
found in large masses ; but since extensive plants for its 
extraction are not necessary, this is not a vital objection. 
The future of this ore seems good; for, with the develop- 
ment of the southern states, a large, undeveloped supply 
will no doubt be drawn upon. 

Red Hematite Ores. — This mineral, which in 1880 produced 
but 1.5 per cent more ore than magnetite, and only 5 per 



iron. 123 

cent more than brown hematite, in 1891 produced 63.9 
per cent of all the iron ore of the country. Out of a total of 
14,591,178 tons of iron ore produced in 1891, 9,327,398 tons 
were red hematite. This remarkable increase is due chiefly 
to the development of the Lake Superior and Alabama 
districts, while at the same time, and for the same reason, 
the output of magnetite decreased. 

One of the most remarkable deposits of iron in the world 
is the Clinton ore bed which occurs in a horizon in the 
upper Silurian, known as the Clinton, because of its typical 
occurrence at Clinton, New York. This bed is not always 
ore-bearing, but in many parts of the outcrop it is a lime- 
stone interstratifled with shales and limestones. On the 
other hand, it is frequently iron-bearing. It occurs in New 
York state, extends southward, following the folds of the 
Appalachians to Alabama, and is found outcropping in 
Wisconsin, Ohio, and Kentucky. Throughout its extent 
it occasionally furnishes iron mines. The ore varies in 
character, being at times oolitic, when it is called flaxseed 
ore, or, in other places, replacing fossils, and then being 
called fossil ore. 

There is some question as to the origin of this remarkable 
ore-bearing stratum. It has been held that the ore was 
originally precipitated during the formation of the stratum, 
and the oolitic character of certain parts of the bed seem to 
prove this. On the other hand, fossils, which were originally 
calcareous, are now composed of hematite, which shows that, 
in these cases at least, the ore is a replacement, and hence 
secondary. At Atalla, Alabama, the Clinton limestone, two 
hundred and fifty feet from the surface, carries only 7.75 
per cent of iron, while at the outcrop it has 57 per cent of 



124 ECONOMIC GEOLOGY OF THE UNITED STATES. 

iron, and this seems to prove that here the ore is concen- 
trated by the action of weathering, which has removed some 
of the calcite. Probably in different places the ore has 
originated differently. It is not unlikely that, for some 
reason, during the time of deposit of the Clinton bed, abun- 
dant iron was precipitated, producing a ferruginous lime- 
stone and, in places, even an oolitic iron bed. Later, perco- 
lating water removed some of the iron, and a replacement of 
fossils and limestone took place, partly from this source and 
partly from an outside supply of iron. The replacement 
may have been at first siderite and later hematite. Thus the 
bed varies in character and richness from place to place, 
owing to the local concentration, and perhaps, also, as at 
Atalla, as the result of the concentrating effect of weathering. 
The Lake Superior hematites are even more important 
than the Clinton ore bed, but their occurrence is less simple. 
There are several districts in Michigan, Wisconsin, and Min- 
nesota. In the Marquette district of Michigan, the ore 
occurs in strata of quartzites, schists, banded jasper, and 
limestones of Huronian age (a division of the Archean). 
There are several types of occurrence, but all are apparently 
bedded with these strata. As to their origin, Foster and 
Whitney x considered them eruptive, Brooks and Pumpelly 2 
called them altered limonite beds ; and the last geologists to 
study the ore, Irving and Van Hise, 3 ascribe the origin of 
the ore deposits in part to concentration by percolating 
water, in part to a replacement of limestone. This view 

1 Report on the Geology of the Lake Superior Land District, Part II., 
1851, pp. 65-69. 

2 Geological Survey Michigan, 1869-1873. 

3 The Penokee Iron-bearing Series of Michigan and Wisconsin, Tenth 
Annual Report United States Geological Survey, pp. 341-508. 



IKON. 



125 



seems the most probable, although it is possible that other 
explanations may account for some of the deposits. The 
Menominee district in the same region has a very similar 
mode of occurrence. Owing to the studies of Irving 
and Van Hise, the occurrence of the ore in the third 
district, the Penokee-Gogebic, is well understood. Here 
the rocks are cherty 1 limestones, slates, quartzites, etc., 



It D 



OpOi 










"o *° °o \' !/'/<"> 
6 oeVBOngea 




Fig. 15. —Diagram showing mode of occurrence of iron ore in Penokee region. 
a, quartzite stratum ; b, dikes ; c, iron ore, replacing ferruginous chert, e ; 
t, drift. (Modified from Irving and Van Hise.) 



dipping at a moderate angle and crossed by trap dikes. 
It has been shown by these authors that beds of dolo- 
mitic limestone, originally stratified with the series, have 
been replaced by red hematite, and that the ore occurs most 
commonly in the troughs formed by the intersection of the 
dikes with the impervious strata beneath the replaced lime- 
stones (Fig. 15). The water apparently percolated through 
1 Chert is impure flint. 



126 ECONOMIC GEOLOGY OF THE UNITED STATES. 

the limestone, but its progress was retarded by the nearly 
impermeable quartzites with which the limestone was bedded 
and by the dikes which crossed the strata. The water being 
forced to stand here, the limestone was slowly replaced by 
the iron obtained by solution from the rocks through which 
the water had percolated. 

A part of the same general series of iron ores is found in 
Minnesota, in the Vermilion Lake and Mesaba Range dis- 
tricts. Here, as in Michigan and Wisconsin, although the 
ore is sometimes magnetite, it is chiefly hematite. The prob- 
able origin of these ores is by replacement, as in Michigan, 
although Winchell, 1 who has studied the district carefully, 
believes them to be originally precipitated, together with 
many of the associated rocks, from an ocean of pre-Cambrian 
age when the waters were in a transition stage from the 
heated primary ocean to the cold sea of geologic times. This 
theory, while very enticing, does not seem as yet to be suffi- 
ciently supported by facts for its general acceptance. 

One of the most interesting deposits of iron in America 
is the famous iron mountain of Missouri. Here is a hill of 
porphyry, rising, dome-shaped, through the much younger 
Silurian rocks. In the porphyry there are veins of hematite, 
probably of secondary origin, although some have held that 
they are an original part of the erupted rock. The ore sup- 
ply comes, however, from the base of the hill, where it occurs 
as a conglomerate cemented by limestone and resting upon 
the porphyry. It is overlain by limestone, and the entire 
series dips away from the mountain as if deposited upon a 
sloping surface. No other satisfactory explanation seems 

1 The Iron Ores of Minnesota, Bull. No. 6, Minnesota Geological Survey, 
1891. 



ikon. 127 

possible than that suggested by Pumpelly, 1 which is, that 
this hill of porphyry was, in the Silurian period, covered by 
a soil of disintegration, in which the pebbles of iron, obtained 
from the veins, remained while the porphyry was decayed 
to a clay. As the sea which formed the Silurian strata 
encroached upon this hill or island, the clay was removed 
and the iron pebbles formed into a conglomerate at the shore 
line and later covered with other sediments. 

The ores of hematite are all apparently bedded. This 
appearance is either due to actual bedding by deposition, or 
to the subsequent alteration of some previously bedded iron 
ore of another character (such as limonite), or to the con- 
centration of the ore by some process, usually by replace- 
ment. These deposits are frequently lens-shaped, and often 
attain a considerable thickness in the centre of the lens. 
Frequently the hematite mines are open works, although 
where the beds are of a more permanent character, tunnels 
and shafts are constructed, generally in continuation of 
previous open-work mining. 

Magnetite Ores. — In 1891, 15.88 per cent of the iron ore 
produced in the country was magnetite, or out of the total 
of 14,591,178 tons of ore, 2,317,108 tons were of this nature. 
At present magnetite is the third most important ore of iron, 
while in 1880 it held second place, and was only a little over 
one per cent behind the leading ore, hematite. In distribu- 
tion, the magnetite is found chiefly in the metamorphic rocks 
of New York, Pennsylvania, New Jersey, and Michigan. 
Practically all of the New Jersey ore is magnetite, and in 
both New York and Pennsylvania this is the most important 
of the iron minerals. 

1 Geological Survey of Missouri for 1872, Part I. 



128 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Magnetite is found in nearly all eruptive and metamor- 
phic rocks, as an accessory constituent, in small grains origi- 
nally formed with the other minerals. It rarely occurs in 
eruptive rocks in sufficient quantities to pay for mining, 
although a deposit of titaniferous iron ore, which has been 
worked at various times, is found in an eruptive rock in 
Rhode Island. The usual mode of occurrence of magnetite 
as an ore is typical. It exists as lenses in metamorphic 
rocks, frequently in the Archean, and often associated with 
limestone. This mode of occurrence is fully illustrated in 
New Jersey, in the Archean Highlands, where there is so 
much magnetite, both as disseminated particles and beds, 
that the ordinary compass is of no use in the region. These 
mines have been developed since the last century, and there 
are thousands of prospect and mine holes, of great and small 
size, where the dip-compass has indicated the presence of 
magnetite and encouraged exploration. The beds of iron 
are associated usually with black hornblendic bands and 
appear to be bedded with the gneiss, although the apparent 
bedding of both the gneiss and the iron may be secondary. 
In the mines the strike is quite uniformly to the northeast 
and the dip usually southeast, though sometimes northwest, 
and generally there is, in addition to this, a " pitch " in the 
direction of the strike, as if the rocks had been folded across 
the strike. The ore is very irregular, occurring sometimes 
in pockets, swelling and pinching, and at times being faulted. 
Some of the veins, as for instance the Hibernia mine of the 
central Highlands, are remarkably uniform and extensive, 
but many are so local and irregular that it has been neces- 
sary to abandon them. Owing to the distance from coal, 
the irregularity and uncertainty of the iron deposits, and the 



IRON. 129 

fact that the largest and most uniform have already been 
worked to a considerable depth, these New Jersey magnetites 
are rapidly losing in importance ; and unless by taking advan- 
tage of the magnetic properties of the ore, some process of 
concentration is perfected, the iron industry of New Jersey 
must continue to decline. The peculiar occurrence of frank- 
linite on the western border of the Highlands is described 
under zinc. 

At Mineville, Chateaugay, and other mines in New York, 
the occurrence of the magnetite is very similar to that of New 
Jersey. In the Chateaugay mine, as is often the case in the 
Archean ores, the magnetite grades, by an increased admixture 
of gangue, into the barren gneiss of the country. The Mine- 
ville deposit which has been worked to a depth of three hun- 
dred feet has, since it was opened in 1824, produced up to the 
close of 1889 over 9,500,000 tons of ore. In this mine the 
variation in character of the ore, which is even more marked 
in some other magnetite mines, is well shown. Practically 
all of the Archean magnetite, unlike the brown or red hema- 
tite, is hard and granular, or semi-crystalline. The iron 
percentage is high and varies in the Mineville ore from 
55 to 70 per cent. In the New Bed of this mine a good 
Bessemer ore is found in which the percentage of phospho- 
rus does not exceed 0.025 per cent ; but in one of the old 
openings the amount of phosphorus varies from 0.5 to 2.5 
per cent, owing to the presence of apatite. There is practi- 
cally no sulphur in this ore, but in some magnetite deposits 
there is so much sulphur, usually in the form of iron pyrite, 
that the ore is not mined. Where magnetite is free from 
both sulphur and phosphorus, on account of the high per 
cent of iron, it is a valuable ore. 



130 ECONOMIC GEOLOGY OF THE UNITED STATES. 

To account for these deposits of Archean magnetite, vari- 
ous theories have been offered. An intrusive origin has 
been suggested at various times, and certain facts have been 
stated which seemed to corroborate this view ; but, without 
discussing this theory, it may be stated that there are no 
facts connected with magnetite deposits which cannot be 
easily explained by other theories, and that there are numer- 
ous objections to this hypothesis which have not been an- 
swered. A second theory is that the magnetite beds are, in 
part at least, altered beds of limonite deposited with the 
original materials out of which the gneiss has been pro- 
duced, and metamorphosed to magnetite when the gneisses 
were formed. While it cannot be denied that this is a pos- 
sible source of some of these deposits, it may yet be said that 
it does not seem to be a general explanation. Moreover, the 
gneisses are so much altered that their original character has 
never been determined, and without proof this explanation 
can be called little else than a guess. That some of the 
Archean magnetites are replacements of limestone beds 
seems certain, and in some cases is proved; but even this 
plausible explanation, when applied to the New Jersey mag- 
netite, does not seem to be of general application. A fourth 
theory, and the one which, taking into consideration all the 
facts, seems to the writer most probable, is that of segre- 
gation ; but in advancing it there is no intention of denying 
absolutely the other explanations. The proofs upon which 
this belief rests can hardly be stated here. It may be noted, 
however, that magnetite is present in grains throughout 
most of these gneisses, and that it is gathered together into 
strings, bands, and even beds, just as is the hornblende and 
augite of the gneisses. There seems to be every gradation 



IRON, 131 

from the magnetite grain to the magnetite bed, and it 
appears to be the result of metamorphism and the gathering 
together of like minerals from the surrounding rocks during 
their alteration ; that, in other words, it is merely an expres- 
sion of metamorphism of rocks rich in iron ; but whether 
these rocks were originally limonite-bearing shales or diabase, 
we cannot in the present state of our knowledge determine. 

A very peculiar deposit of magnetite is found in Cornwall, 
Pennsylvania, occurring in an entirely different position from 
the above. Here an extremely wide regularly stratified deposit 
of iron, with a width of more than 400 feet, rests against a 
trap rock, which has protected it at this point from destruc- 
tion by weathering, forming a series of hills instead of the 
valleys which would normally have resulted in this soft de- 
posit. Whether it was originally a pyritiferous shale which 
has been altered, or a brown hematite metamorphosed to 
magnetite, seems a question. 1 It is a phenomenal example of 
cheap mining, the ore being soft so that very little explosive 
is needed, and the mine being entirely an open-work. Walls 
of ore eighty feet high are blasted with dynamite. Owing to 
the great width of the deposit, it can be exploited in a series 
of retreating terraces at the base of which temporary tracks 
are laid for its removal. Already, up to 1891, 11,508,990 
tons of ore have been won from this deposit, which was first 
opened in 1740 ; and there are no signs of exhaustion, but 
on the contrary boring showing that the ore extends below 
the water line. 

Magnetite is typically a metamorphic mineral. As this 
ore by rusting alters to the hydrous forms of iron ore, so 

1 Professor Lesley states that the deposit is a replaced lime-shale. Sum- 
mary, Final Report, Vol. I., Pennsylvania Geological Survey, pp. 351-357. 



132 ECONOMIC GEOLOGY OF THE UNITED STATES. 

they by metamorphism lose their superfluous constituents 
and become magnetite. Thus, in whatever original position 
other ores of iron are found in sedimentary strata, magnetite 
is also found in the same mode of occurrence in the meta- 
morphic rocks which are altered from these sediments. It 
has, therefore, the appearance of bedding, and sometimes 
really is bedded, though more often this appearance is the 
result of replacement or concentration, by the process of 
segregation, during metamorphism. 

Carbonate of Iron Ores. — This is the least important of the 
ores of iron, and in 1891 out of the total output of 
14,591,178 tons of iron ore, only 189,108 tons, or 1.3 per 
cent, of the ore of the country was carbonate. In 1880 the 
carbonate of iron produced 11.57 per cent of the total out- 
put, or, during the year, 823,471 tons. At present the only 
important carbonate-producing state is Ohio, which in 1891 
had an output of over 100,000 tons ; New York, Kentucky, 
Pennsylvania, and Maryland being the only other producers 
of this ore. 

The carbonate, siderite, may be considered to be a combina- 
tion of iron and calcite in which the percentage of iron varies 
even to the point of complete replacement of the calcium. 
It occurs as concretions of clay ironstone in beds of calcare- 
ous clay ; but in this form it is usually too disseminated for 
mining in this country, although in Europe it is extensively 
mined. As an ore it is found stratified with slates and sand- 
stones in the Burden mine, near the Hudson, in New York, 
and it is quite universally found stratified in the other mines, 
being apparently most frequently a stage in the replacement of 
limestone beds. The blackband ore of Ohio and Kentucky 
is a stratified carbonate, coloured black by bituminous matter. 



IKON. 133 

An exception to this general statement is found in a mine 
at Roxbury, Connecticut, now abandoned, where the ore is 
found in a fissure vein with quartz, galena, and calcite, — 
quite an exceptional mode of occurrence. 

Foreign Occurrences. — Foreign occurrences of iron illus- 
trate the same general features as those described above, 
and very little need be said about them. The greatest iron- 
producing country in the world, next to the United States, 
is Great Britain, which, up to 1889, was a greater producer 
than this country. At the time of the Roman conquest, 
iron mines were opened in the Forest of Dean and else- 
where, and some of these mines are still worked. Through- 
out the United Kingdom iron ores occur bedded in regular 
strata, or gathered together along contacts, or in hollows. 
These ores are chiefly red and brown hematite and the 
carbonate. They occur in the Carboniferous or mountain 
limestone, and in the coal measures chiefly; in the latter 
place being found in the form of clay ironstone concretions, 
which sometimes coalesce into partial beds. Brown hema- 
tites are found also in the Mesozoic strata. Many of the 
iron ores of the United Kingdom are of very low grade, and 
are capable of being profitably mined only because of the 
close association with coal, the coal and iron ore being at 
times hoisted to the surface through the same shaft. In 
1860 the United Kingdom produced 8,155,749 metric tons 1 
of iron ore, and the output increased to 1880-1882, when 
the annual production amounted to over 18,000,000 metric 
tons. Since then the output has been steadily decreasing, 
until in 1891 it amounted to only 12,987,159 metric tons. 

1 The metric ton is 2204 lbs. ; the long ton, 2240 lbs. ; the short ton, 
2000 lbs. 



134 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Germany, the third in rank as an iron-producer, had an 
output in 1891 of 10,857,521 metric tons of ore. These ores, 
which sometimes occur in thick beds, are found chiefly 
in the Devonian and Jurassic strata in the form of limonite, 
hematite, and the carbonate. The typical occurrence is 
bedded, but the ore also occurs in veins often at contacts. 
Spain, which in 1892 produced 5,465,150 metric tons, is a 
producer chiefly of brown and red hematite which occurs in 
Cretaceous rocks. The most important district of this 
country is Bilbao, which in 1890 produced 4,326,933 metric 
tons, or nearly the entire output of the country. In order 
to show the importance of our own iron-producing regions, 
it may be stated that, in 1890, the total output of Spain, the 
fourth iron-producing country in the world, was more than 
650,000 tons less than the output of the one state of 
Michigan. 

Austria, which has been an iron-producing country since 
the Roman invasion, illustrates very nearly the same occur- 
rence as the above, and in 1891 produced 1,231,248 metric 
tons. Belgium also produces hematite, limonite, and clay 
iron-stone, which is bedded in and below the coal. In 
1891 the output was only 202,204 metric tons. Both 
Norway and Sweden produce considerable iron, chiefly 
magnetite, the ore from the latter country being remark- 
able for the very low percentage of phosphorus, that 
from Dannemora containing only 0.003 per cent, and from 
other provinces, varying up to 0.05 per cent. This makes a 
remarkably good Bessemer steel, and the output of iron ore 
from Sweden in 1891 was 987,405 metric tons. In both 
Norway and Sweden, as in other parts of Europe where the 
rocks are metamorphic, the occurrence of the iron ore is 



iron. 135 

in lenses, apparently of segregated origin, very nearly the 
same as the ores of Xew Jersey and the Adirondacks. Both 
Italy and Portugal have large stores of iron, but owing to 
the fact that there is no coal at hand, very little is mined in 
these countries, Italy having an output in 1891 of only 
216,486 metric tons. ■ Canada has iron in modes of occur- 
rence similar to that of the United States, although, owing 
to the great areas of Archean rocks, it is probable that 
magnetites predominate over the other ores. There are 
undoubtedly great possibilities in store for the iron industry 
of Canada, although the general absence of coal over large 
areas must always interfere with its development. At 
present, Canada produces very little iron, the output for 
1891 being only 62,591 metric tons. The iron ores of Africa, 
Asia, Australia, and South America are practically unde- 
veloped, not from a lack of supply, but because of the lack 
of industrial progress. The countries of these continents 
allow their stores of iron to remain undeveloped, obtaining 
only a very little for pressing local needs, and depend upon 
the United States and Europe, Great Britain chiefly, for the 
greater part of their iron supply. China, which produces 
not far from 500,000 tons a year, is an exception to this 
statement. 

General Mode of Occurrence. — Iron ores occur dissemi- 
nated through all rocks, being usually magnetite in the 
igneous and metamorphic rocks, and hematite, limonite, or 
carbonate in the sedimentary strata. From one or another 
of these sources it is taken into solution by water and either 
precipitated (bog-iron ore), or segregated (some of the New 
Jersey mines), or caused to replace other rocks (Penokee- 
Gogebic region), or, under some circumstances, formed into 



136 ECONOMIC GEOLOGY OF THE UNITED STATES. 

beds by disintegration and mechanical deposition (Iron 
Mountain, Missouri). Under all of these circumstances an 
actual or apparent structure of bedding, either original or 
secondary, is typically given to iron-ore deposits. Varia- 
tions from this type of occurrence are distinctly rare. Fre- 
quently the beds of ore are very wide, and, unlike most of 
the ores to be considered, the process of mining is usually 
by open works instead of in true mines. 

Uses of Iron. — The uses of iron are so varied and im- 
portant that civilization depends upon it more than upon 
any other mineral product of the earth. Indeed, without a 
plentiful supply of iron the civilization of the present could 
hardly have been attained ; and, where iron is not present, a 
high degree of advancement in art and industry is not 
quickly reached. How much England and the United 
States owe to their supplies of iron can probably never be 
told. 

The value of iron in the arts depends upon the fact that 
it is both abundant and cheap, and that, by subjecting it to 
different processes, it can be made either brittle or malleable, 
either soft or extremely hard, and either comparatively 
fragile or extremely tough. Not only can its properties of 
hardness be varied by heat and tempering, but also, by alloy 
with such metals as chromium or nickel, a steel of extreme 
hardness can be produced. The melting-point may also be 
varied. If iron melted as easily as lead, or was as refractory 
as platinum, it would be of but little use, yet, for some pur- 
poses, it is desirable to have a comparatively low, or, on the 
other hand, a high, melting-point, and this can be accom- 
plished within a certain range, by different processes. Iron 
can in one form be cast, thus making it very valuable in 



iron. 137 

a certain class of work, but in another form, where more 
durability is desired, it is worked by hammering and weld- 
ing instead of by casting. There is one great fault in iron, 
and that is the ease with which it rusts ; but by painting or 
coating with some less easily oxidized metal, as tin or zinc, 
to exclude the air, this is not so serious an evil as it might 
at first thought seem to be. 

The uses of iron are being extended every year with the 
advance of civilization and the decrease in cost of iron and 
iron-working. No single industry has called for a greater 
supply than the railroads, and now steel vessels are demand- 
ing an increasing quantity. These, with bridges and great 
engineering works, are the largest uses for iron ; but in the 
smaller articles for household, farming, and other similar pur- 
poses, great quantities are also used. It is hardly probable 
that the marvellous increase in demand for iron, which has 
taken place in the past twenty-five years, will be repeated in 
the next quarter of a century, although there is little doubt 
that there will still be a decided increase. 

Distribution of Iron Ores. — The ores of iron are widely dis- 
tributed in this country, yet the areas in which mines are 
located are extremely limited. East of the Mississippi and 
a line projected northwards to the Lake of the Woods, the 
output of iron ore in 1889 amounted to a total of 96.73 per 
cent of the entire product of all the mines in the country. 
If this eastern division be divided by an east and west line 
extending along the Ohio and Potomac, the product of the 
northern portion, according to the census of 1890, is 76.82 
per cent of the total output of the United States. While 
this rather remarkable distribution is in part due to the geo- 
logical conditions, it is chiefly the result of the fact that the 



138 ECONOMIC GEOLOGY OF THE UNITED STATES. 

industrial progress of this section has been greatest. Un- 
doubtedly the two conditions have been interacting, the 
increase in industrial demands calling for more iron, while, 
on the other hand, the presence of the supply has without 
question aided in the progress. Ten years ago this division 
was much more marked, and already the centres of the iron 
supply are moving southward and westward ; and, as these 
sections develop industrially, their stores of iron will be more 
and more called into use. 

Carrying the consideration of iron-ore distribution to a still 
smaller division of areas, one is impressed by the fact that 
workable deposits are extremely local. The four iron-bearing 
ranges of the Lake Superior region are all included in a semi- 
circle, with a radius of 135 miles and a centre in Lake Supe- 
rior, the greater part of the mines being near the periphery. 
In 1889 this district produced 7,519,614 tons 1 of ore. A 
parallelogram sixty miles in length and twenty miles in 
width would include all the mines of the Lake Champlain 
district of northern New York, from which, in 1889, 779,850 
tons of ore were won. A circle of fifty miles' radius, em- 
bracing portions of Alabama and western Georgia, included 
mines which, in 1889, produced 1,545,066 tons of ore, and a 
single locality, Cornwall, Pennsylvania, contributed 769,020 
tons. From these districts alone, 10,613,550 tons, or 73.11 
per cent of the entire output of iron ore of the United 
States, were obtained in 1889. 2 

During the year 1891 the four states, Michigan, Alabama, 
Pennsylvania, and New York, each produced over 1,000,000 

1 Long tons are used in the statistics for the United States. 

2 The facts in this paragraph were obtained from the volume on Mineral 
Industries of the Eleventh Census Reports, p. 9. 



IRON. 139 

tons of ore ; and Michigan had an output of over 6,000,000 
tons ; Minnesota, Virginia, Wisconsin, Tennessee, and New 
Jersey each produced over 500,000 tons, and less than 
1,000,000 ; Georgia, Colorado, Missouri, and Ohio each pro- 
duced between 100,000 and 500,000 tons. Thus thirteen 
states only may be considered important iron-producing 
states, and of these only one is in the Cordilleran region. 

Reviewing hurriedly the output of each of these states, it 
is found that Michigan has, in -1891, decreased its output 
over 1,000,000 tons since 1890, but still produces 41.99 per 
cent of the iron ore of the country. Of this ore, 88.87 per 
cent was red hematite, 7.47 per cent brown hematite, and 
3.66 per cent magnetite. More than one-half of the red 
hematite of the country comes from Michigan. The several 
districts which produce this ore are situated on the peninsula 
between Lakes Superior and Michigan ; and more than three- 
fourths of it comes from nineteen mines, five of which, in 
1891, produced over 300,000 tons each, four between 200,000 
and 300,000 tons, and ten between 100,000 and 200,000 tons. 

The development of the iron industry in the various dis- 
tricts of the Lake Superior region since 1883 is shown in the 
table on page 140. 

Alabama, the second state as an iron-producer, continues 
to increase its output, and in 1891 the production was 
1,986,830 tons, or 13.62 per cent of the iron ore of the 
country. The ore is chiefly red hematite, although about one- 
fourth was brown hematite, and in both the red and brown 
varieties it is the second most important producing state, its 
output of red hematite being 16.35 per cent of all produced 
in the country, and of brown hematite 16.76 per cent. 
There are six mines in Alabama which produced over 



140 



ECONOMIC GEOLOGY OF THE UNITED STATES. 





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IRON. 141 

100,000 tons of iron ore in 1891, and from one mine, the 
Tannehill mine in Jefferson County, in an area of two acres, 
115,563 tons of brown hematite were produced. In 1880 
Alabama produced only about 171,000 long tons of ore ; in 
1885 the output reached 500,000 tons; in 1888 about 
1,000,000 tons were obtained; and now (1891) the state 
produces nearly 2,000,000 tons, the greater part of which 
comes from the vicinity of Birmingham. 

All four kinds of ore were produced in 1891 by Pennsyl- 
vania, making a total of 1,272,928 tons, or 8.72 per cent of 
the output of the country. Of this, 727,299 tons were mag- 
netite, giving to Pennsylvania the second rank as a producer 
of this ore, or 31.39 per cent of all produced in the country ; 
of brown hematite the output amounted to 363,894 tons, giv- 
ing to the state fourth place as a producer of this ore ; of red 
hematite only 162,683 tons were produced; and of the car- 
bonate 19,052 tons. The output of magnetite and brown 
hematite has decreased since 1890, while that of red hema- 
tite and carbonate has increased. In 1891 the only mine in 
Pennsylvania which produced more than 100,000 tons was 
that of Cornwall, from which the magnetite supply is 
obtained. Many mines in Pennsylvania have been closed 
either because of leanness, excess of phosphorus, or expense 
of exploitation, which prevents competition with the cheaply 
mined and transported ores of other sections. 

New York is the only state, other than Pennsylvania, 
which produced all four ores of iron, and here, also, the 
greater part of the ore is magnetite. In 1891, 782,729 tons 
of magnetite were produced, out of a total of 1,017,216 tons 
of iron ore, which gives to New York first rank as a producer 
of this class of ore. The brown hematites come chiefly from 



142 ECONOMIC GEOLOGY OF THE UNITED STATES. 

the eastern part of the state in a region known as the Salis- 
bury district of New York, Massachusetts, and Connecticut ; 
the red hematites are found in the central and northern por- 
tions ; the carbonates occur at the Burden mines on the 
Hudson ; and the magnetites in the Lake Champlain, western 
Adirondack and southeastern Archean districts, the first 
being the most important district. 

Minnesota advanced from sixth place in 1890 to fifth 
place in 1891, producing then 945,105 long tons of red 
hematite, in which it ranks third as a producer. Although 
all of the ore obtained during 1891 came from three com- 
panies in the Vermilion Range, much prospecting was done 
in the newly discovered Mesaba Range, and it is reported 
that companies with a total capitalization of $75,000,000 
were formed to open up the remarkable deposits of limonite, 
hematite, and magnetite, which occur there. The future of 
this district seems very promising, for the ore is both of 
good quality and quantity, and already in 1892 the region 
began to produce ore. Nearly all of the ore of Virginia is 
brown hematite, of which there were 653,342 long tons in 
1891 of the total output of 658,916 tons of iron ore for 
the state. Virginia takes first rank as a producer of this 
ore, supplying 23.69 per cent of the country's total, and the 
output is increasing. While these ores, which come chiefly 
from the Shenandoah valley, have not a high per cent of iron, 
they are easily smelted and make good iron, but they are 
not suited for Bessemer steel. 

Wisconsin has decreased its output of iron by nearly 
400,000 tons since 1890, and in 1891 its output was only 
589,481 tons, causing it to drop from fifth to seventh place. 
Nearly all of the ore is red hematite, coining from the end of 



IRON. 143 

the Menominee and Gogebic ranges, which extend over the 
line of Michigan into this state. There are extensive 
deposits of brown hematite near the Mississippi, but as 
yet these have been only slightly developed. Tennessee 
produced 543,923 tons of iron ore in 1891, an increase of 
16.80 per cent over the preceding year. Of this, 396,883 
tons were of red hematite, which has increased since 1890, 
and the balance brown hematite, in which the state has 
decreased its output. The red' hematites come from the 
eastern portion of the state in the valley of the Tennessee 
River. Over 98 per cent of the iron ore of New Jersey is 
magnetite from the mines of the Archean Highlands, some 
of which, as the Dickerson, have been operated since early 
in the last century (the Dickerson since 1713). This mine, 
together with others in New Jersey, has been closed since 
1891. Although New Jersey has steadily decreased its out- 
put for a number of years, there was an increase of 6.01 per 
cent in 1891, when the output was 525,612 tons ; but the years 
1892 and 1893 will undoubtedly show a marked decrease. 

Georgia, Colorado, Missouri, and Ohio, each decreased their 
output of iron ore from 1890 to 1891. The ore of Georgia 
is chiefly (82.04 per cent) brown hematite, with some red 
hematite. Colorado also produces chiefly brown hematite 
(89.46 per cent in 1891), with some red hematite and magne- 
tite, the chief supply from this state being used as a flux 
in smelting. Only about 7 per cent of the ore of Missouri 
is brown hematite, and the balance is red hematite. Missouri 
continues to decline as an iron-producer, though not because 
of the exhaustion of its mines. The most important mine 
of the state is the Iron Mountain, which since 1847 has con- 
tributed 3,349,086 tons of ore. All of the iron ore output 



144 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



of Ohio is the carbonate, and the iron industry of this state 
continues to decline owing to the poverty of the ores and 
the competition of the Lake Superior mines. 

During the year 1891 the supply of red hematite came 
chiefly from the four following states named in the order 
of importance, each of which produced over 500,000 tons: 
Michigan, Alabama, Minnesota, Wisconsin ; of brown hema- 
tite, from the five following states, each of which produced 
over 200,000 tons : Virginia, Alabama, Michigan, Penns}d- 
vania, Georgia ; of magnetite, from the four following states, 
in each of which the output was over 200,000 tons : New York, 
Pennsylvania, New Jersey, Michigan ; of the carbonate only 
one state, Ohio, produced more than 100,000 tons, and the 
other carbonate-producers were unimportant. 

Production of Iron. — In the United States the develop- 
ment of the iron industry is shown in the following table 
for the six leading states : — 



PRODUCTION OF IRON ORE IN THE UNITED STATES. 
Long Tons (2240 Lbs.). 





1850. 


1860. 


1870. 


1880. 


1891. 


Michigan .... 


2,700 


114,410 


859,507 


1,640,814 


6,127,001 


Alabama 


1,838 


3,720 


11,350 


171,139 


1,986,830 


Pennsylvania . . . 


877,283 


1,351,000 


2,337,286 


1,951,495 


1,272,928 


New York .... 


46,385 


151,378 


446,945 


1,126,900 


1,017,216 


Minnesota .... 










945,105 


Virginia and West \ 
Virginia .... J 


67,319 


28,109 


84,108 


217,448 


665,116! 



The following table shows the change in rank of the 
iron-producing states since 1850 : — 

1 In 1891 West Virginia produced only 6500 tons. 



IRON. 



145 



1850. 


1860. 


1870. 


1880. 


1891. 


Pennsylvania 


Pennsylvania 


Pennsylvania 


Pennsylvania 


Michigan 


Ohio 


Ohio 


Michigan 


Michigan 


Alabama 


Kentucky- 


New York 


Ohio 


New York 


Pennsylvania 


New Jersey 


Michigan 


New York 


New Jersey 


New York 


New York 


New Jersey 


New Jersey 


Ohio 


Minnesota 



Thus, Michigan, Alabama, and Minnesota have shown a 
remarkable increase since 1870, Pennsylvania a marked de- 
crease, and New Jersey, Ohio, and Kentucky have also 
decreased. The transfer of the iron industry from the north- 
ern Appalachians to the Lake Superior and Alabama regions 
is very striking. In 1889 Michigan produced 40.34 per cent 
of the iron ore, Alabama 10.82 per cent, Pennsylvania 10.75 
per cent (in 1870 Pennsylvania produced 44 per cent), and 
New York 8.59 per cent, the four states combined producing 
70.5 per cent of the total output of the country, four- 
sevenths of which came from Michigan. 

The production of iron ore in the United States in the 
decades since 1850 is as follows : — 

PRODUCTION OF IRON IN THE UNITED STATES SINCE 1850. 

1850 1,560,442 long tons. 

1860 2,396,485 " " 

1870 ...... 5,250,402 " » 

1880 7,489,464 " » 

1890 16,276,584 " " 

1891 14,591,178 " « 

While the United States exports considerable iron ore, it 
imported in 1892 only about 800,000 tons, and has never 
imported in any one year much over 1,000,000 tons. The 



146 ECONOMIC GEOLOGY OF THE UNITED STATES. 



imported ore comes chiefly from Spain, Algeria, and Cuba, 
and is used almost entirely for Bessemer steel. 

PRODUCTION OF IRON ORE IN THE WORLD. 



United States . . , 
Great Britain . . . 
Germany and Luxem- 
burg 

Spain 



1889. 



14,518,041 
14,546,105 

11,002,187 
5,067,144 



1890. 



16,276,584 
13,780,767 

11,409,625 
5,788,000 



1891. 



14,591,178 long tons i 
12,987,159 metric tons 

10,657,521 " " 
4,822,080 2 " 



The total production of iron ore for the world in 1890 was 
approximately 55,000,000 long tons. In 1890 the United 
States took first rank as an iron-producing country, sup- 
plying 28.9 per cent of all the iron ore of the world. From 
this iron ore, 9,353,020 metric tons of pig iron were produced 
and 4,346,932 tons of steel, no allowance being made for the 
imported ores. The total value of the iron ore produced in 
the United States in 1890 was $33,364,958. 

1 Long tons, 2240 lbs. ; metric tons, 2204 lbs. 

2 The output of Spain has increased in 1892 to 5,465,150. 






CHAPTER VII. 

GOLD AND PLATINUM. 

Gold. 

General Statement. — The gold product of the world comes 
chiefly from native gold, which, in most cases, exists either 
in quartz veins or in gravels resulting from the decom- 
position of gold-bearing rocks, and the separation and accu- 
mulation of the debris by running water. Aside from this 
source there is, however, a large supply furnished as a by- 
product in silver and copper mining, and also a smaller supply 
from mines of other metals. So far as we know, the greater 
part of the gold from this source is mixed mechanically and 
without chemical combination, unless an alloy be considered 
a chemical rather than a mechanical mixture. All of the 
gold which is called native contains silver in alloy (usually 
from 8-10 per cent), as well as smaller quantities of other 
metals, and much of the silver ore is gold-bearing. The two 
industries of gold and silver mining are therefore intimately 
related, and are often considered together ; but it seems well 
here to discuss the two metals separately. 

Appalachian Gold Fields. — Prior to the year 1848, when 
the gold of California became an important element of our 
mineral wealth, the gold of the country came chiefly from 
the southern states, which produced over 11,000,000 worth 
a year, but which now, in 1892, have a total output of only 
1306,015.96. This marked decrease was due first to the 

147 



148 ECONOMIC GEOLOGY OF THE UNITED STATES. 

exodus of the miners to the new fields, and later to the inter- 
ference of the Civil War ; but the gold industry thus para- 
lyzed, again became important in 1870, and since then the 
output has been slowly increasing, excepting during the past 
few years, when there has been a slight decline. The gold 
in this section comes chiefly from South Carolina, Georgia, 
and North Carolina, where it occurs in the belt of talcose 
schists which extend east of the Appalachians proper from 
these southern states into Canada, being auriferous for the 
greater part of the distance, although usually with such a 
small percentage of gold that it cannot be profitably ex- 
tracted. If there were ever placer deposits in the northern 
states along this belt, these were swept away by the glacial 
invasion; but in the southern states placer deposits were 
found and worked, at first, then mines were opened in the 
schists, and now, owing to the introduction of the advanced 
methods of reduction of the more refractory ores, these mines 
are below the water line. Of the seventy-one mines in opera- 
tion in these states in 1889, thirty-one were in North Caro- 
lina, twenty-two in Georgia, and seven in South Carolina. 
Three of these mines produced over $20,000 worth of gold, 
and ten between $10,000 and $20,000 worth. It will be 
seen, therefore, that these mines are not very extensive nor 
valuable, although from the seven gold-producing states of 
this section, there has been produced, between the years 
1799 and 1891, about $44,000,000. 

California Quartz Mines. — With the discovery of gold in 
California, there was a transfer, not only of the industry, but 
also of the miners themselves, from the extreme east to the 
extreme west of the country. Not only was there an exodus 
of miners, but hordes of totally inexperienced men travelled 



GOLD AND PLATINUM. 149 

to the new gold placers, until, at the close of 1850, it is esti- 
mated that there were not less than 50,000 men in the gold 
fields, many of whom earned from 11000 to $5000 a year, 
while some became wealthy almost in a day. The history of 
the excitement of these times, of the development of crime 
and its suppression, the suddenly made and equally suddenly 
lost fortunes, and the hopes which were never fulfilled, forms 
a most interesting chapter in the history of the nation, a par- 
allel of which has probably never before existed. The west 
developed with wonderful rapidity from an uninviting almost 
desert region, occupied by savages, to its present state of 
civilization, although even now the effects of these condi- 
tions are still manifest in many places ; and, indeed, some of 
the very conditions themselves are still present in some parts 
of the west. It may be said that the west was literally 
created by the discovery of gold, followed by that of silver 
and other metals, and the necessary development brought 
about by these discoveries. Nor are the effects confined to 
the Avest ; for the country as a whole has been greatly bene- 
fited by the production of these vast stores of mineral 
wealth. 

At first the rush was all to the newly discovered gold 
fields of California, but soon the prospectors found that there 
were almost equally rich fields in the intervening territories, 
and the base of their operations spread rapidly over the 
whole area of the Cordilleras. Superficial stream gravels 
first attracted attention, then the older gravels were dis- 
covered, and soon the source of the gold itself, in the rocks, 
was explored, and now the chief supply of the gold comes 
from these permanent and original sources. 

In California the gold occurs in the Jura-Trias slates of 



150 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Mesozoic age, which are folded to form the Sierras and ex- 
tend as highly tilted strata in a nearly north and south direc- 
tion parallel to the axis of these mountains. These slates 
are traversed by quartz veins extending in general parallel- 
ism with the strike and dip of the rocks, but not strictly 
so. The largest of these, the so-called " Mother Lode," is 
a great quartz vein, outcropping boldly as a ledge above the 
surface, like a great white wall, and extending parallel to 
the axis of the Sierras for a distance of seventy or eighty 
miles from Mariposa to Amado. It is not, strictly speaking, 
a continuous vein, nor is it everywhere productive, but it 
varies in width from six to sixty feet, and consists of a series 
of veins, pinching-out or ending in offshoots, with frequent 
barren spaces. Other smaller veins are found in general 
parallelism with this. At the surface the quartz is semi- 
transparent or translucent and usually iron-stained by the 
rust of the decayed iron pyrite which it originally contained. 
Below the water line the quartz is found to contain iron 
pyrite, copper pyrite, zinc blende, galena, and other minerals ; 
and in all of these sulphides, as well as in the quartz itself, 
gold is found, sometimes in flakes and grains, but often in 
microscopic quantities. By the decay of the sulphides, cavi- 
ties, usually iron-stained, are formed, and in these, as also in 
the quartz itself, the gold is found in the surface ledges. 
The typical surface gold-bearing veinstone in this region is 
therefore a cellular, iron-stained, translucent quartz. 

This was the first ore discovered by the gravel-washers, 
who, rinding that the placer deposits occurred locally, natu- 
rally looked about for the source of the gold. The discovery 
of these ores marks the second stage in the development of 
the gold. industry of the west. When the auriferous quartz 



GOLD AND PLATINUM. 151 

ledges were mined and crushed, and extensive hydraulic 
works established for washing gravels on a large scale, the 
individual prospector began to be replaced by mining com- 
panies, although, even to this day, the prospector may still 
be seen washing the stream gravels in California and else- 
where in the Cordilleras. With the establishment of com- 
panies, extensive plants were constructed for crushing the 
quartz and removing the free gold by concentration and 
amalgamation; but when the water line was passed and the 
undecomposed sulphides encountered, new methods needed 
to be introduced, and the third or present state of the gold- 
mining industry of California was reached. 1 Low-grade ores 
of this nature carry from $3.50 to $8.00 of gold per ton, and 
high-grade ores yield from $15.00 to $30.00, while the aver- 
age is probably from $10.00 to $12.00 a ton. By the new 
and more economical processes, ore which a few years ago 
was considered worthless, can now be worked, since nearly 
everything is saved, whereas formerly much gold was wasted. 
It was for this reason that miners believed that the ore 
decreased in quantity as the lode extended into the earth. 

The description of this mining region applies almost 
equally well to the majority of the mines of the country, 
and, indeed, of the world, where the ore is primarily gold. 
Still, at times, the gold is found in other occurrences, as, 
for instance, in the Spanish mine at California, where it 
occurs in a bed of steeply dipping soft slates, which are 
traversed in every direction by small quartz veins. Here 

1 A very complete description of these processes of gold reduction, the 
chlorination and cyanide processes, will be found in The Mineral Industry, 
etc., 1892, Rothwell, pp. 233-270. A very good description of the general 
process of gold-mining and reduction may be found in the Eleventh Census 
volume on Mineral Industries, pp. 103-108. 



152 ECONOMIC GEOLOGY OF THE UNITED STATES. 

the metal exists not only in the quartz, but also in the clay- 
partings between the veins and the country rock, and even, 
in small quantities, in the slate itself. In El Dorado County 
there is another mine, the Dalmatia, which is worked at low 
cost owing to the softness of the rock, in which the occur- 
rence of the gold is slightly irregular. A band of chloritic 
schist, having a width of about 125 feet and bounded by 
clay slate, is crossed by gold-bearing quartz veins ; and the 
entire rock is so badly decayed and so soft that, owing to its 
width, the deposit is quarried in an open pit. Both the 
quartz and the schist are obtained and crushed, and the mine 
pays although the rock carries only from $1.50 to $2.00 
worth of gold to the ton. 

What the origin of these gold deposits is cannot be defi- 
nitely stated. For many years the " Mother Lode " has been 
used as a typical illustration of the segregation type of vein ; 
but recently 1 it has been proved that the vein crosses the 
slates at an angle to the structure, and is therefore unlike a 
typical segregation vein. Yet it has never been shown that 
his lode is a true fissure vein, and it is surely not an eruptive 
deposit. In spite of the recent observations it still seems 
that these quartz veins must be of segregation origin. The 
rocks in which they occur were deposited in Mesozoic 
times and have been metamorphosed to their present condi- 
tion by the folding of the Sierras, of which they form a part. 
It seems not unlikely that the quartz veins are one of the 
results of this metamorphism ; and the fact that the gold is 
found also in the enclosing slates and schists seems to indi- 
cate that it was originally a part of the sediment out of 

1 Fairbanks, Geology of the Mother Lode Gold Belt, Am. Geologist, 1891, 
Vol. VII,, pp. 209-222. 



GOLD AND PLATINUM. 153 

which these rocks were built, having been during their meta- 
morphism gathered together in flakes and tiny bits both in 
the rocks and in the quartz veins which have been formed. 
Exactly the same process is seen in many slates where, by 
metamorphism, iron pyrite is gathered into crystals and 
accumulations of crystals, both in the massive slates and along 
the cleavage and joint planes, as well as in veins of quartz 
and calcite which traverse the slates. Although it cannot 
be said that we definitely understand the process by which 
the gold has been accumulated, it may be stated that the 
process of segregation seems best to account for all the facts 
observed. 

California Auriferous Gravels. — By the disintegration of 
the slates and quartz veins through a long period of time, 
the more easily destructible minerals, together with the light 
but chemically durable quartz, have been carried off, while 
the heavy, indestructible gold has in part remained behind 
and accumulated in the river gravels. These placer deposits 
are of two kinds, — those which have accumulated in recent, 
and those which were formed in old and now extinct river 
beds. During the Tertiary period the Sierras, which had 
then attained much of their growth, were subjected to long- 
continued denudation, the rocks were gradually worn away, 
and an extensive series of well-developed valleys were 
formed, extending from the mountains out upon the plains 
at their base. It thus happened that by a process of natu- 
ral hydraulic concentration gold was accumulated in these 
valleys, particularly on the more level plains at the base of 
the mountains where the river currents were slackened. 
But for a subsequent change, however, these accumulations 
might have been gradually swept seawards and have been 



154 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



lost. During the close of the Tertiary period the remarkable 
outburst of volcanic activity, which extended over the entire 
Cordilleras, and has only in recent times ceased, sent floods 
of lava out upon the surface and these naturally sought the 
valleys as the easiest direction of flow. Thus many of the 
valleys were flooded with lava, which forced the streams to 
carve new channels, and which, when it cooled, formed a 
durable protection to the soft and easily removed gravels. 
As the result of subsequent erosion the river valleys were 
chiefly formed at the side of the lava flows, and because of the 



-c 



c-^ 




Fig. 16. — Cross-section of Table Mountain, California, showing auriferous gravels 
(G), beneath basalt (B). P, pipe clay; T, tunnel; C, continuation of ancient 
valley; A, slates; R, recent river containing gold-bearing gravels. (After 
Whitney.) 

hard lava-capping, the old stream beds became lava-capped 
hills consisting in part of gold-bearing gravels 1 (Fig. 16). 

These buried ancient river gravels are now mined, partly 
by hydraulic means, partly by tunnelling ; and the gold is 
found, just as in the modern valleys, in spots, or in "pay 
streaks," in what are called " pay gravels " in distinction 
from the unremunerative gravels which predominate and 
contain either very little or no gold. The gravels are some- 
times from 150 to 250 feet thick, and in the famous Table 
Mountain of Tuolumne County the basalt covering is 150 

1 These were once supposed to be marine gravels, but are now known to 
be river gravels because of their structure, character, and fossil contents. 



GOLD AND PLATINUM. 155 

feet thick. Five conditions have therefore conspired to bring 
these accumulations of gold-bearing gravels into their present 
position : (1) the chemical decomposition of the iron pyrite 
and the mechanical destruction of the auriferous quartz; 
(2) heavy valley grades in the mountains and a decreasing 
slope on the plains ; (3) large quantities of water ; (4) a long- 
continued time for action ; (5) the protection from subsequent 
destruction furnished by the basaltic lava flows. 

Partly by the working over of these old river gravels 
in the new streams, and partly by a new supply furnished 
them by the subsequent disintegration of the gold-bearing 
rocks, the placer deposits which were first discovered, and 
which exist in all of the states and territories of the Cor- 
dilleras, were formed. The amount of gravel which has 
been washed by hand and by hydraulic processes can be 
realized only by actually visiting the region. Millions of 
dollars' worth of gold have been taken from single wash- 
ings, and cities (such as Helena, Montana) have been built 
upon the sites from which the metal was won. Associated 
with the gold in the gravels, platinum and the precious 
stones, diamond, topaz, and sapphire, have been occasion- 
ally found, although until recently no systematic opera- 
tions for their recovery have been instituted. 

At first the gravels were washed by hand, but it was 
not long before such a simple process was found to be too 
slow a road to wealth, and the prospectors invented the 
process of hydraulic mining (Frontispiece) 1 in imitation of 

1 Descriptions of the gold fields, particularly of the gold gravels, and 
the mode of extracting the metal from them, will be found in Whitney's 
Auriferous Gravels, Metallic Wealth of the United States, The United 
States, pp. 309-389 ; and also in the Eleventh Census volume on Mineral 
Industries, pp. 106-108. 



156 ECONOMIC GEOLOGY OF THE UNITED STATES. 

the more extensive but very similar method of concentra- 
tion which nature had long made use of in accumulating 
the gold gravels. A stream of water is led to the gravel 
deposit and directed against the bank, washing the debris 
into sluices, where the gold collects behind riffles, and is 
held in amalgamation by mercury, while the lighter minerals 
and fragments of rock pass onward. In order to obtain 
sufficient water and a sufficient force, pipes are con- 
structed, often for a distance of many miles and at great 
expense, bridging valleys, passing through tunnels, and 
even crossing divides. Where the hydraulic mines have 
been abandoned, these expensive works still remain, in 
many places the only sign of the former gold-mining 
operations, if we except the stream bed littered with 
gravel, and the partly destroyed gravel banks. Sometimes 
towns, which grew up almost in a day, are now found 
abandoned near these deposits. 

An ingenious contrivance known as the hydraulic elevator 
is sometimes used for washing gravels situated in low places. 
By means of this the gravel is forced up hill by a powerful 
current of water, and then the gold is obtained. 

Hydraulic mining in California very quickly found an 
enemy in the farmer who dwelt upon the stream below 
the sluices ; for, by the immense amount of gravel which 
was washed into the streams, their farming lands and farm- 
ing operations were seriously interfered with, and it soon 
became a question which should survive in these places, 
the farmer or the miner. The question was settled in 
1884 in favour of the farmer by an injunction, issued by 
the United States Circuit Court, which caused many of the 
hydraulic mines to suspend operations; and more recently 



GOLD AND PLATINUM. 157 

this has been extended by state legislation adverse to the 
hydraulic mining industry. Owing to this set-back, hydrau- 
lic mining fell to a comparatively unimportant place in 
the gold-producing industry of California, while at the 
same time quartz mining increased. Within a year or 
two, the Circuit Court having modified its injunction, a 
number of the abandoned hydraulic mines have commenced 
operations again, and the future of this industry seems good. 
It is now proposed to construct dams below the sluices, 
under the direction of government engineers, and thus, by 
forming catchment basins, to save the farmers from the 
flood of sediment and its destructive effects. 

Origin of Nuggets. — In placer deposits the gold is found 
chiefly in small flakes and grains, but sometimes large 
pieces called "nuggets" are discovered. It has been sug- 
gested that they are formed by some chemical change 
during or after the accumulation of the gravels, but for 
various reasons this seems improbable. The most probable 
origin of nuggets is by actual derivation from the quartz 
veins, although perhaps their size has been increased by 
the welding of one fragment to another as they pass 
down stream in company with small pebbles, and even 
large boulders. A gold mass weighing 500 ounces has been 
found in one of the quartz veins in Victoria; but this is 
small compared with the two large nuggets from the same 
region, one of which, the "Welcome Stranger," weighed 
2280 ounces, and the other, the " Welcome Nugget," which 
contained 2166 ounces of gold and ten pounds of quartz 
and other gangue minerals. That they are derived from the 
veins seems shown by the fact that they usually contain 
some quartz, and that they are generally rounded as if rolled 



158 ECONOMIC GEOLOGY OF THE UNITED STATES. 

about in the stream. The discrepancy in size suggests the 
welding of fragments of gold, although it does not prove 
it, for large nuggets are rare, and the gold gravels repre- 
sent in a small space the accumulations from the destruction 
of large areas of quartz, while the actual mining opera- 
tions in the veins are of comparatively limited extent. It 
is possible therefore that fragments as large as the largest 
nuggets may yet be found in the quartz veins. 

Other Western Gold Fields. — The other states and ter- 
ritories of the Cordilleras have gold-bearing gravels and 
auriferous quartz in very nearly the same mode of occurrence 
as in California, and it would be mere tedious repetition to 
describe other mines of this region, although there are some 
points which need to be mentioned. Colorado is second 
in importance as a gold-producing state and ranks first 
as a producer of the precious metals. Both placer and 
quartz mines are worked there, some of the latter being 
free-milling and some mixed with sulphides, just as in 
California. A very considerable percentage of the Colorado 
gold comes from the silver mines, from which it is produced 
as a by-product. South Dakota, chiefly the Black Hills 
district, also produces gold from the same sources, and here 
also there is an interesting occurrence of gold in Cambrian 
sandstone derived from the disintegration of the Archean 
rocks in early Palaeozoic times. Montana, Nevada, Idaho, 
Oregon, Arizona, New Mexico, and the other states and 
territories of the Cordilleras illustrate the same modes of 
occurrence, but here the output is less than from the above- 
mentioned states. In Montana, in addition to the placer 
and quartz deposits, there is much gold produced as a by- 
product from the silver and copper mines. 



GOLD AND PLATINUM. 159 

Nevada continues to fall in importance as a gold as 
well as a silver producing state. The greater number of 
the mines of Nevada, aside from those on the Comstock 
Lode, are silver mines, and hence the chief gold supply 
from this state comes from the Comstock. This mine, which 
is described in the chapter on silver, in 1891 had an 
output of only $1,200,000 of gold, although at one time 
the output exceeded $14,000,000 in a single year (1877), 
and between the years 1859 and 1891, inclusive, there has 
been produced from this lode $140,771,979 of gold. Aside 
from the occurrences of gold described above, in all the 
states and territories this metal is found in eruptive rocks, 
porphyries, granites, diorites, etc., sometimes disseminated 
and sometimes in quartz veins which traverse them, chiefly 
in the latter. Gold, is also found as the telluride, but the 
typical mode of occurrence in the rocks is in the native 
state associated with sulphides in quartz veins traversing 
metamorphic and igneous rocks. 

Such wonderful "bonanza" mines as the Comstock are, 
of course, liable to be found at almost any time, but at 
present there are none in operation. In all of the states and 
territories new mines are being opened, and many of these, 
together with the older ones, are being operated upon an 
economical and scientific basis. On the whole, although 
the output of gold is not rapidly increasing, it has in the 
past decade more than held its own, and the future seems 
very promising. The bright outlook for the future of gold is 
increased by the recent disastrous drop in the price of silver 1 
and the consequent suspension of operations in some of the 
mines, which will serve to direct the energies and capital of 

1 The fall in price in the early summer of 1893. 



160 ECONOMIC GEOLOGY OF THE UNITED STATES. 

many from silver to gold production. The industry of 
gold mining may now be said to be more than a mere 
speculation, or a game of chance, for it has become a 
business, as safe, where properly managed, as any other 
mining industry. 

Alaskan Gold Mines. — One of the most striking develop- 
ments of gold mining in this country, in the past ten years, 
is the opening of the Alaskan fields. For a number of years 
prospectors have panned gold from the rather limited gravels 
of this region, but it has been within only a very few years 
that actual mining operations have been begun. Now mines 
are opened in many parts of the territory, but chiefly along 
the coast line. The prospectors are now at work in the 
interior, in the valley of the Yukon, and they report valuable 
deposits of gold in this region ; but mining there is difficult, 
owing to the shortness of the season, the cold and disagree- 
able weather, and above all the difficulty of obtaining a food 
supply. At present the most important district in Alaska is 
Douglas island, where the Treadwell mine is situated. Here 
placer deposits were discovered in 1881, and upon their re- 
moval a low-grade gold-bearing quartz was found beneath. 
The ore and gangue consist of quartz and calcite carrying 
free gold and gold-bearing iron pyrite ; and everything between 
the walls, which are 550 feet apart, goes to the stamp mills, 
the ore being mined, or rather quarried, in large open pits. 
It is worthy of note that 240 stamps are constantly at work 
whenever there is sufficient water, and steps are being taken 
to improve the water supply, so that they may work steadily. 
Other districts are being developed, and there is every 
reason to expect that gold mining will serve as a means 
of opening to settlement a large part of this domain, as it 



GOLD AND PLATINUM. 



161 



did our great western country, with such wonderful rapidity, 
in the middle of the century. 

The following table shows the remarkable development of 
the industry in Alaska, but it does not represent the actual 
output of gold, since many individual placer-miners carry 
their gold to San Francisco. 

PRODUCTION OF GOLD IN ALASKA. 



1880 


$6,000 


1884 


$200,000 


1888 


$850,000 


1881 


15,000 


1885 


300,000 


1889 


904,000 


1882 


150,000 


1886 


446,000 


1890 


762,000 


1883 


300,000 


1887 


675,000 


1891 


900,000 



Foreign Gold Regions. — Australasia. Second in . impor- 
tance to the United States is the Australian gold region, the 
discovery of which followed closely upon the opening of the 
California fields. In 1851 gold was first discovered in Vic- 
toria, and until 1856, when the richer alluvial deposits began 
to be exhausted, the output rapidly increased; but since 
then there has been a decrease in production, although the 
quartz mines have increased in number and product. Dur- 
ing the years 1855 to 1857 the output was in each year 
over £ 11,000,000 sterling, but in 1891 it was only about 
£ 2,300,000 sterling. As yet the methods of ore reduction 
are not as advanced as those of the United States, so that 
the full capacity of the mines is not fairly tested, and 
because of insufficient slope the process of hydraulic mining 
is not extensively used. There are several districts in Vic- 
toria, of which two, Ballarat and Sandhurst, are the most 
important. The mode of occurrence varies slightly, but 



162 ECONOMIC GEOLOGY OF THE UNITED STATES. 

bears a marked resemblance to that of California, the gold 
being found in auriferous quartz, old river gravels, and new 
river gravels. Usually the quartz veins traverse diorite, 
granite, and sandstone, but the rocks are of Palaeozoic 
instead of Mesozoic age, as in California. It is supposed 
that the quartz veins are of segregated origin, and that the 
supply of gold comes chiefly directly from the eruptive 
rocks. Both the recent and ancient (Tertiary) river gravels 
very closely resemble those in California, the latter even to 
the fact that they are covered by lava flows. Here, how- 
ever, owing to the difference in erosion, the gravels are 
exploited by means of shafts, instead of tunnels, and the 
mines are drained by pumps so that gravel mining is much 
more difficult here than in California (Fig. 17). From all 
the mines in Victoria, between the years 1851 and 1891 
inclusive, £229,787,892 sterling of gold have been produced. 
New South Wales has gold occurrences of almost exactly 
the same character. Here gold is also found in the consoli- 
dated conglomerates of the Carboniferous period, showing 
that at this time conditions of accumulation existed which 
were very similar to those prevailing in the Tertiary period. 
From this country, in the forty-one years succeeding 1851, 
the gold product has been worth £ 38,633,489 sterling. In 
New Zealand the same occurrences are noticed, and, in addi- 
tion, some gold is obtained from the seashore sands. The 
river gravels are sometimes consolidated, and it is then nec- 
essary to crush them as in the case of the quartz and the 
Carboniferous conglomerate. Since 1857 to the close of 
1891 New Zealand has supplied gold to the amount of 
£47,433,077 sterling. Gold is found in Queensland in 
quartz veins traversing Devonian slates as well as in gravels, 



GOLD AND PLATINUM. 



163 



and this country has produced ,£28,052,199 sterling of gold. 
Tasmania has gold in the same modes of occurrence, and 
although the output is comparatively small, the future seems 
good. South and Western Australia are also gold-producing 
regions, but they are of less importance than the other sec- 
tions. Although at present Australasia is second in impor- 
tance to the United States as a producer of gold, there have 
been years since 1851 when the United States was of second 
rank. Yet the total output of gold from the entire Aus- 
tralasian region which, between 1851 and 1891 inclusive, 




Fig. 17. — Section showing the position of the gold-hearing gravels in New South 
Wales. A, gold-bearing gravels; B, basalt; C, clay strata; P, Palaeozoic 
strata. 

amounts to 11,690,137,137 is somewhat less than the output 
of the United States for the same period of time. 

Russia and Siberia. — Before the discovery of gold in Cali- 
fornia, in 1848, the Russian empire held first place as a gold- 
producing region ; but it soon fell to second rank, and after 
the discovery of gold in Australia, to the third place, which 
it now holds. The production of gold in the Urals began in 
1745, from the placer deposits in 1774, and since 1822 the 
output from the placers has exceeded that from the quartz 
mines. In eastern Siberia gold was discovered in 1704, and 
placers in 1829. Since then, this, the most important gold 



164 ECONOMIC GEOLOGY OF THE UNITED STATES. 

district of the Russian empire, has been chiefly a region of 
placer mining. There is also an important district in the 
Altai Mountains in western Siberia, and gold is produced 
also in Finland and in the Caucasus Mountains. Gradually 
the mining centre has been transferred from west to east, the 
source being chiefly recent river gravels, new deposits being 
discovered as old ones were exhausted. The quartz veins 
which are iron pyrite bearing, and occur in highly inclined 
crystalline schists, are exploited on a very moderate scale, 
but with the introduction of improved methods and machin- 
ery these will doubtless be more thoroughly developed and 
become an important source of gold. Russia, in 1822, pro- 
duced 1585,703 worth of gold, and this output increased 
gradually to $9,000,000 in 1842, since which time it has been 
gradually increasing, with some fluctuations, until 1891, 
when the product amounted to 124,131,500. During the 
years between 1878-80, inclusive, the annual output ex- 
ceeded 128,000,000, and in 1883 dropped to a little over 
$19,000,000. 

South African Fields. — A most important gold field has 
been very recently developed in South Africa. This field 
was discovered in 1884, in the Transvaal, and active opera- 
tions were begun in 1886, since which time the district has 
literally jumped into the fourth place as a gold-producer, and 
promises to reach a still higher position. Here, in nearly 
vertical strata of sandstones and shales, are beds of conglom- 
erates, varying in colour and texture and being frequently 
auriferous. Some of these beds are 200 feet wide, separated 
by thin quartzite partings, both rocks being auriferous. 
Above the water line the gold is free, but below this it is 
found in pyrite, and the chlorination process has been intro- 



GOLD AND PLATINUM. 165 

duced for its reduction. It is predicted that this region will 
continue to rapidly increase its output ; and the phenomenal 
development shown in the following table lends probability 
to this prediction. The output from the South African gold 
fields since 1887 is as follows : — 

1887 $755,212 

1888 3,817,118 

1889 7,834,663 

1890 9,315,651 

1891 14,414,993 

1892 22,128,051 

Total $58,265,688 

Of this output, the greater part comes from one district, 
the Witwatersrand, which in 1892 produced 121,190,085, and 
of the total has produced all but about $5,500,000. Some 
gold is found in other parts of Africa, and no doubt this 
metal will be discovered in the interior if there are any 
mountains of metamorphic rocks. 

Other European and Asiatic Countries. — Although nearly 
all European countries produce some gold, none besides 
Russia are of much importance in this respect. Austria 
supplies some gold as a by-product from the antimony and 
silver mines. Hungary is of much more importance in this 
respect, and the greater part of this metal accredited to 
Austria-Hungary comes from the latter. Here the quartz 
veins occur in eruptive rocks, usually in porphyry, of 
Tertiary age. A very little gold is produced in Germany 
as a by-product from the silver and other mines, but this 
country is of very little importance in this respect. Con- 
siderable gold is smelted in Germany (in 1891, $2,141,998), 



166 ECONOMIC GEOLOGY OF THE UNITED STATES. 

but a large part of this is foreign ore sent for smelting from 
South America and elsewhere. In Asia, China is next in 
importance to Siberia, as a gold-producing country, but we 
know little about its occurrence. Japan also produces some 
gold, but next to China, British India is most important. 
There are several gold fields, but only one, the Mysore 
province, is of much importance. Here the ore is found in 
quartz veins in trap dikes which traverse metamorphic rocks. 
Between the years 1888 and 1892 the output of India 
increased from $650,866 to 12,955,620, the greater part of 
which came from Mysore. 

South American Countries. — South America, which, during 
the sixteenth and seventeenth centuries, was of such impor- 
tance as a source of the precious metals, has fallen in rank, 
and is now of little importance in influencing the world's 
supply, although there are still good stores awaiting develop- 
ment when the social conditions become more stable. At 
present, Colombia and Chili are the only important gold- 
producing countries on this continent; but Peru, Brazil, and 
Bolivia each produce some. Since 1537 Colombia has had 
an average annual output of gold exceeding $1,000,000, and 
often exceeding $3,000,000. More gold has come from this 
country than from any other in South America, — between 
the years 1537 and 1891 the product having amounted to 
nearly $900,000,000. Brazil has produced gold since the 
seventeenth century, and its total output has been not far 
from $700,000,000 or $800,000,000. Between the years 1741- 
1760, the average annual output exceeded $9,000,000, al- 
though it is now less than $1,000,000. Bolivia, although a 
producer of gold since 1545, has never had a great output, 
the annual average rarely exceeding $1,000,000 ; but the total 



GOLD AND PLATINUM. 167 

production since 1545 is probably not far from 1200,000,000. 
The annual output of gold in Chili since 1545 has frequently 
exceeded 11,000,000, but Peru has been of less importance. 
Before the discovery of America, there was considerable gold 
in circulation in both Europe and Asia, 1 the supply having 
come chiefly from the latter continent. Soon, however, the 
New World became the source, and until the present century 
the supply came chiefly from South America. It is probable 
that since 1545 considerably more than 82,000,000,000 worth 
of gold have been produced in South America. The mode 
of occurrence of this metal in these countries is very 
similar to that of the gold elsewhere, and needs no especial 
description. 

Mexico and Canada. — Mexico has been a surprisingly 
unimportant producer of gold; but when the similarity of 
the Mexican and Cordilleran geology is considered, we are 
forced to conclude that this is due, not to the lack of supply 
of gold, but rather to the character of the people and their 
failure to discover and work the deposits which must exist. 
The country has never produced much ; but when the indus- 
trial conditions of this republic have been improved to the 
modern standard, and inaccessible regions have been opened 
to exploration, it may be expected that a development of 
mineral wealth very much like that of our own country will 
result. Very nearly the same remarks hold for Canada, 
although this country is somewhat in advance of Mexico. 
In 1863 Canada produced over $4,000,000 worth of gold, but 
the output has steadily decreased since then to only 1925,486 
in 1891. At present only a small supply comes from the 

1 One estimate places the amount in circulation in Europe in 1492 at 
$193,000,000, and in Asia, $1,500,000,000. 



168 ECONOMIC GEOLOGY OF THE UNITED STATES. 

western provinces and from Nova Scotia, where the gold is 
found in the Cambrian slates and quartzites in iron pyrite 
bearing quartz veins. The Canadians have been remarkably 
tardy in exploring their western reserves, but the little 
exploration which has been done has shown the existence 
of valuable deposits of the precious metals. Since gold is 
found in all of the states from Mexico to Canada, including 
the borders states, Montana, Idaho, and Washington, and also 
in Alaska, it may be safely predicted that the intervening 
territory is also gold-bearing. As yet no important develop- 
ments have been made, but no doubt the next fifteen or twenty 
years will witness marked changes in this respect. 

Origin of Gold Deposits. — In review, attention should be 
called again to the remarkable uniformity of occurrence of 
gold. Perhaps the greater part of the supply cOmes from 
gravels of Tertiary or Recent age, formed from the disinte- 
gration of gold-bearing rocks and veins, and accumulated by 
reason of the greater specific gravity and durability of the 
gold. Allied to these deposits is what is perhaps the third 
most important mode of occurrence ; namely, in consolidated 
gravels of an age greater than the Tertiary. These were, 
prior to the development of the South African gold fields, 
illustrated in Australia by the gold-bearing Carboniferous 
conglomerates, in the Black Hills by the auriferous Cambrian 
sandstone, and by other similar deposits elsewhere ; but now, 
owing to the development of the South African fields, this 
class of gold occurrence has become of great importance. 
Whether these conglomerates are of marine or river origin 
cannot be said, although it seems probable that future studies 
will prove that they were originally river gravels worked 
over by the sea. Our information concerning these fields is 



GOLD AND PLATINUM. 169 

extremely meagre ; and any statement of origin must, there- 
fore, be tentative. Still, their apparent uniformity of extent 
indicates marine origin, and the quantity of gold suggests 
the intervention of rivers ; for although it is possible that 
they may have resulted from the destruction of gold-bearing 
rocks by the ocean waves, it seems much more probable that 
they represent a deposit, not unlike the auriferous gravels of 
California, hurriedly "worked over by a sea encroaching upon 
a sinking land. 

The second most important mode of occurrence, or per- 
haps even the most important, is in auriferous-quartz, asso- 
ciated with iron pyrite. There seem to be two types of this 
occurrence, the one connected with eruptive rocks, the other 
with sedimentary strata ; and in both cases segregation ap- 
pears to be the method of accumulation. There can be little 
doubt that the original condition of the gold was in dis- 
seminated form in eruptive rocks and that when associated 
with eruptive rocks these were generally the immediate and 
primary source. Where bedded with and occurring in sedi- 
mentary strata, such as slates, it is very probable that the 
gold was placed first in the slates by the disintegration of 
eruptive or other gold-bearing rocks, and later gathered 
together from this secondary source. Since gold occurs dis- 
seminated in eruptive, sedimentary, and metamorphic rocks, 
it is natural to expect that it will be found in other classes 
of deposits than those of segregation origin. The author 
knows of no case where any other origin than that of segre- 
gation is proved, in which gold is the primary product ; but 
the fourth important source of gold — namely, that of associ- 
ation with deposits of other metals — furnishes illustrations 
of this class of deposits which are gold-bearing. 



170 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Why gold, as the primary ore, is not found in other modes 
of occurrence than segregation (excepting the mechanical) 
is difficult to explain, although it may be due to the fact that 
this metal forms practically no combinations with mineralizers, 
and, being nearly insoluble, is taken into solution only in 
small quantities, and forms, therefore, but a small proportion 
of the mineral contents of those veins in which the minerals 
are more soluble. During metamorphism the agents at work 
are more powerful, and gold may therefore be segregated, 
together with iron pyrite, quartz, and other minerals in 
smaller quantities. In any event there is an intimate rela- 
tion between gold, quartz, and iron pyrite. This theory is 
offered without insisting upon its accuracy, since the true 
solution of the problem may depend upon changes and 
agencies much more difficult of explanation. 

Uses of Gold. — Gold is used almost exclusively for a 
medium of exchange and for show utensils and ornaments. 
The brightness of the metal attracted the attention of the 
early people and savages, who made ornaments from it. Its 
rarity has added to its value for this purpose and has caused 
gold to be adopted as a medium of exchange, in and between 
nations, since very early times. In a rough way gold was 
used for this purpose even in Homeric times, and when 
Csesar invaded Great Britain he found gold coins in circula- 
tion among the Britons. Aside from these uses, gold is 
employed to a considerable extent in dentistry and in an 
alloy for the better class of gilding ; but ordinary gilt paper 
contains no gold. 

In the arts the use of gold depends upon its brightness, 
freedom from tarnish, and remarkable ductility and mallea- 
bility, which permit it to be easily worked. Pure twenty- 






1 



GOLD AND PLATINUM. 171 

four carat * gold is entirely too soft for use, and all that we 
use is alloyed with other metals. Even free gold in nature 
is never pure, but generally has from eight to ten per cent 
of silver in alloy. By alloying with silver and copper the 
coinage and ornamental gold is made harder, but this is 
rarely more than eighteen carat gold, and usually much less. 
Coloured gold, which is sometimes used in fancy jewelry, is 
made by alloy with different metals. With copper a dark 
yellow and reddish yellow is produced, the intensity of the 
colour varying with the percentage of copper. Silver and 
gold make a greenish and pale yellow metal, and iron gives 
to gold a grayish colour. An extremely small percentage of 
lead makes gold brittle and destroys its ductility, and an 
alloy of gold, palladium, silver, and copper makes a brownish 
red compound which is so hard that it is used for bearings 
in fine watches. 2 

It is in coinage that gold finds its most important use, and 
it is a striking fact that from the very earliest times this 
metal has remained of value for this purpose, notwithstand- 
ing the remarkable fluctuations in production. When gold 
began to be produced abundantly from California and Aus- 
tralia, in the decade following 1850, it was predicted that 
this would necessitate a reorganization of the currency of 
the world. During the decade 1831-40 the mean annual 

1 Gold alloys " are considered as consisting of so many carats to the unit, 
the pound or half pound being divided into twenty-four carats, each of which 
contains twelve grains. What is termed eighteen carat gold is a unit of 
twenty -four carats of alloy containing eighteen carats of gold and six of 
copper." — Braxnt, Metallic Alloys, p. 331. 

2 Brannt's Metallic Alloys is a valuable reference book for a description 
of the alloys of different metals, and Hiorns' Mixed Metals will also be found 
of value in this connection. 



172 ECONOMIC GEOLOGY OF THE UNITED STATES. 

product of gold in the world was 20,289 kilogrammes, during 
1841-1850 the annual average was 54,759 kilogrammes, and 
between 1851-1855 the average was 199,388 kilogrammes per 
year. But all the gold produced has been easily absorbed, 
partly because of the increase of business between nations, 
and partly by reason of the increasing demand for gold in 
the arts. Whereas a half-century ago only the wealthy 
could afford gold utensils and ornaments, now these, either 
in plated or solid form, find their way among even the poorer 



The gold coinage of the mints of the United States has 
fluctuated remarkably since the Union was formed. Before 
1833 it reached 81,000,000 in only one year (1820), but 
since then more than 81,000,000 dollars have been issued 
each year. Since 1850 the coinage has never, in any one 
year, fallen below 814,000,000, and in 1863 it reached 
883,000,000, and in 1881 896,000,000. In 1892 the gold 
coinage amounted to 834,787,222.50. The four leading 
gold-coining countries in 1891 issued gold as follows : Great 
Britain 832,720,633, United States 829,222,005, Australia 
(considered as a whole) 826,389,044, Germany 814,277,220. 
No other nation issued more than 84,000,000 of gold. In 
1889 the United States exported nearly 851,000,000 of gold, 
of which 8 38,000,000 was domestic. In 1892 over 876,- 
000,000 of gold were exported, and 817,000,000 imported. 
These figures show nothing with reference to the output 
of the country, but they do show the great amount which 
is used for coinage, and the way in which gold passes from 
one country to another by reason of slight changes in value 
or other economic causes. Much of the gold coined in any 
one year is recoined gold. 



GOLD AND PLATINUM. 



173 



Production of Gold. — The following tables give some 
instructive statistics for the gold production of the states, 
the United States, and the world : — 



PKODUCTION OF GOLD IN THE VARIOUS STATES OE THE 
UNITED STATES. 





1877. 


1880. 


1885. 


1887. 


1891. 


California . 


$15,000,000 


$17,500,000 


$12,700,000 


$13,400,000 


$12,600,000 


Colorado . . 


3,000,000 


3,200,000 


4,200,000 


4,000,000 


4,600,000 


Dakota . . 


2,000,000 


3,600,000 


3,200,000 


2,400,000 


3,550,000 


Montana . . 


3,200,000 


2,400,000 


3,300,000 


5,230,000 


2,890,000 


Nevada . . 


18,000,000 


4,800,000 


3,100,000 


2,500,000 


2,050,000 


Idaho . . . 


1,500,000 


1,980,000 


1,800,000 


1,900,000 


1,680,000 


Oregon . . 


1,000,000 


1,090,000 


800,000 


900,000 


1,640,000 



The territories next in rank, all producing between 
1500,000 and $1,000,000, are Arizona, New Mexico, Alaska, 
Utah. The only eastern state producing more than $100,000 

is South Carolina ($125,000). California produces more 

i 
than one-third of the gold of the country, and about one- 
tenth of the product of the world. Since 1881 there has 
been a decrease in the output of this state, and this is in 
part attributable to the legislation adverse to hydraulic 
mining. Colorado is gradually increasing its output of gold, 
and Dakota fluctuates, but remains about uniform with a 
slight increase. Montana reached a maximum in 1887, and 
its output has since declined, while Nevada shows the effect 
of the abandonment of a part of the Comstock Lode, by a 
remarkable decrease between 1878 and 1880. 



174 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



OUTPUT OF GOLD FROM THE UNITED STATES. 
Valued at $20.67 ax Ounce. 

1847 $889,085 

1848 10,000,000 

1849 40,000,000 

1853 . 65,000,000 

1859 50,000,000 

1862 39,200,000 

1866 53,500,000 

1870 50,000,000 

1880 36,000,000 

1890 32,845,000 

1892 33,000,000 

The total production of gold in the United States since 
1792 to the close of 1892 is $1,969,692,949, of which all but 
$24,536,767 has been produced since the beginning of 1848. 
Since 1853 there has been a gradual decrease in the output, 
with some fluctuations. The United States, since the begin- 
ning of 1848, has produced nearly as much gold as South 
America since 1533. It has exceeded the output of Austra- 
lasia by over $300,000,000, and has greatly exceeded the 
output of Russia since 1822. We may, therefore, safely 
claim for the United States the first rank as a gold-producing 
country. 

PRODUCTION OF GOLD IN THE WORLD, 1880-1891. 





1880. 


1882. 


1884. 


1886. 


1888. 


1891. 


United States 


$36,000,000 


$32,500,000 


$30,800,000 


$35,000,000 


$33,175,000 


$33,175,000 


Australasia 


28,765,000 


31,955,017 


28,284,000 


26,425,000 


28,560,660 


31,399,000 


Eussia . . . 


28,551,028 


23,867,935 


21,874,000 


20,518,000 


21,302,000 


24,131,500 


Africa . . . 


1,993,800 


1,993,800 


830,000 


1,438,000 


4,500,000 


14,199,600 


China . . . 






6,222,000 


3,650,000 


9,000,000 


5,330,000 


Colombia . . 


4,000,000 


3,856,000 


3,856,000 


2,500,000 


3,000,000 


3,472,000 


British India . 








421,600 


676,563 


2,495,000 



GOLD AND PLATINUM. 175 

The countries producing between $1,000,000 and $2,000,- 
000 of gold, in 1891, were, in the order of their importance, 
Canada, Chili, Austria-Hungary, British Guiana, Venezuela, 
Mexico. The output of gold from the German smelters, 
in 1891, was $2,141,998, but this was partly from foreign 
sources, and we have no statistics for the gold output of the 
mines. Of the total production of gold in the world during 
1891, which amounted to $125,299,700, the United States 
supplied 26.4 per cent, Australasia 25 per cent, Russia 19.3 
per cent, and Africa 11.3 per cent. Together these four 
regions produced 82 per cent of the gold product of the 
world, and the United States and Australasia produced more 
than one-half of the world's supply. 

TOTAL PRODUCTION OF THE WORLD. 

1849 $27,100,000 

1853 155,500,000 

1869 . 125,000,000 

1875 111,000,000 

1880 108,000,000 

1883 97,000,000 

1885 106,000,000 

1889 120,000,000 

1891 125,299,700 

The mean annual product of gold prior to this time, in 
kilogrammes, valued at $664.60, was, for the period between 
1493-1520, 5,800 kilos.; between 1741-1760, 24,610 kilos.; 
between 1811-1820, 11,445 kilos.; between 1831-1840, 
20,289 kilos. Between the years 1856-1860 it increased to 
201,750 kilos. 



176 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Platinum Grroup. 

Occurrence of Platinum. — Platinum 1 is of little impor- 
tance as an ore in the United States. Occasionally, however, 
it is found in the gold-bearing gravels, but as it does not 
amalgamate with the mercury, it is not saved, and it does not 
seem to be in sufficient abundance to pay for separate mining. 
Nevertheless, some is produced each year, and in 1890 about 
$2500 worth was produced chiefly from the auriferous 
gravels of California and Oregon. Since no especial efforts 
have been made to save it, we have no means of knowing 
whether it is present in sufficient abundance for separate 
mining. The prospectors do not know the value of the 
black sand, nor are they always able to distinguish it from 
less valuable ores; and it is, therefore, not unlikely that 
deposits may yet be found. 

The supply of platinum comes chiefly from Russia, where 
it occurs in gravels, probably originally auriferous, on the 
Siberian side of the Urals, where it was first discovered in 
1819. Since serpentine is usually near at hand, and the 
placers increase in richness as this rock is approached, and 
since the metal has been found in this rock, it seems probable 
that this is the source. This mode of occurrence of platinum 
and the association with serpentiniferous rocks 2 prevails also 
in other platinum-producing regions. Platinum is always 

1 Descriptions of the platinum group and their modes of occurrence will 
be found in The Mineral Industry for 1892, Rothwell, pp. 373-397, and in 
the Eleventh Census volume on Mineral Industries, pp. 341, 342. 

2 Serpentine is generally a metamorphic rock resulting from the decompo- 
sition and alteration of olivine-bearing as well as from other rocks. The 
source is generally, though not always, an igneous rock, and the platinum 
may be a product of this metamorphism. 



GOLD AND PLATINUM. 177 

alloyed with the other metals of the platinum group, iridium, 
osmium, palladium, etc., and with iron, the amount of 
platinum varying from 50 to 80 per cent. In Russia, as well 
as in other platinum-producing regions, chrome iron 1 and 
iridosmium are associated with the metal. 

Next to Russia, Colombia is the most important region as a 
platinum-producer, and about 125 kilogrammes are annually 
supplied from there. Some platinum is also supplied from 
Brazil, Borneo, New South Wales, New Zealand, and British 
Columbia, about $10,000 worth having been produced from the 
latter region in 1891. In all of these countries the platinum 
comes from auriferous gravels, and in some regions it is also 
found alloyed with gold. A unique occurrence discovered in 
Canada a few years ago promised at first to produce platinum, 
but as yet has not done so. This occurrence at Sudbury, 
Ontario, was an arsenide of platinum found in the nickel 
mines of that region. 

Uses. — Platinum is tin-white in colour, very heavy, 
extremely ductile and malleable, and melts only at a very 
high temperature (1750° C). It is very permanent, and only 
a few substances attack it. The first use of the metal was to 
adulterate gold, but until very recently its most important 
use was for crucibles and other chemical apparatus in which 
a high melting-point and chemical permanence are needed. 
It has been used for coinage in Russia, from 1828 to 1845, 
but in the latter year its coinage was suspended and the 
coins called in, because of its increase in value and the con- 

1 It will be noticed by reference to the chapter which considers chrome 
iron, that this ore is always found associated with serpentine, and therefore 
this association of the two minerals is also suggestive of origin from 
serpentine. 



178 ECONOMIC GEOLOGY OF THE UNITED STATES. 

sequent shipment of the metal out of the country. At 
present a considerable part of the platinum used in this 
country is made into pins for holding artificial teeth to the 
plate, this being the only available metal which will with- 
stand the heat of baking. Some platinum is also used in 
dentistry for filling teeth. Incandescent electric lamps and 
other electrical apparatus call now for the greatest supply of 
platinum in the United States, where more of this metal is 
used than in any other country. Some is also used in 
photography and in jewelry. It is estimated that in 1891 the 
United States consumed 1172 kilogrammes in electrical appa- 
ratus ; 1088 kilos, in dental work ; 280 kilos, in sills and 
retorts ; and 92 kilos, in crucibles, dishes, etc. 

Since Russia practically controls the supply of platinum, 
the prices fluctuate greatly. In 1867 the metal was worth 
$4.40' an ounce ; in 1889, about 18.00 an ounce ; then, by a 
corner in the market, the price ran up, in the autumn of 
1889, to 117.50 an ounce. In October, 1892, the price fell 
to 17.50, but in December rose to $10.50. These fluctuations 
in price are not due to a variation in demand or supply, but 
plainly show the intervention of some manipulation on the 
part of those who control the supply. 

Production. — The production of platinum in Russia has, 
since 1878, kept above 2000 kilogrammes a year, but the out- 
put has fluctuated greatly. During 1886, 4316 kilos, were pro- 
duced; in 1889, 2634.8 kilos.; in 1891, 4226. Since 1880 
the average annual output of Columbia has been about 125 
kilos, a year ; from Canada in 1891, 65.4 kilos, were produced ; 
and from the United States, 14 kilos. From Colombia, since 
1737, not far from 18,000 kilos, have been supplied, and 
from Russia, since 1824, about 113,000 kilos. 



GOLD AND PLATINUM. 179 

Other Metals of the Platinum Group. — This grouping is 
based upon the fact that several metals, iridium, osmium, 
palladium, ruthenium, and rhodium, are associated with 
platinum and have the same general properties as elements. 
Iridium, a steel-white, extremely hard metal, next in specific 
gravity to osmium, is supplied partly from its alloy with 
native platinum, and partly from the iridosmium which 
occurs in the platiniferous gravels. It is used for pen points 
and in jewelry (on account of its hardness), in photog- 
raphy, and recently in metal-plating. Osmium, which is 
the heaviest known metal, comes from the same sources as 
iridium, and in the form of iridosmium is used for pointing 
tools and pens. Palladium, a brilliant silver-white metal, 
which also occurs with platinum, is on account of its high 
price very little used, although it has all the attractive- 
ness of silver without its habit of tarnishing. A number of 
small uses are made of this metal, and recently in alloy with 
copper and iron it has been introduced into the manufacture 
of watch springs and balance wheels, for which it is espe- 
cially well adapted, since it is not capable of being magnet- 
ized, and is, therefore, valuable for watches carried in 
electric plants. The two other metals of the platinum 
group, ruthenium and rhodium, are not used in the arts, 
but are practically chemical curiosities. 



CHAPTER VIII. 

SILVEB. 

General Statement. — Unlike gold, there is a wide varia- 
tion in the mode of occurrence of silver, and the ores of 
this metal are both numerous and varied. Native silver, 
although not common, is frequently found, but the most 
frequent occurrence is in chemical combination with mineral- 
izers. The affinity of sulphur for silver is noticed in all 
silverware, which, when sulphurous gases are present, imme- 
diately tarnishes, forming a sulphide. Consequently, in nat- 
ure, silver ores are prevailingly sulphides such as argen- 
tite, pyrargyrite (a sulphide with arsenic), or a sulphide of 
some other metal with silver. Thus the greater number 
of occurrences of the sulphide of lead, galena, much of the 
sulphide of zinc, blende, and the copper sulphide, chalco- 
pyrite, are argentiferous. As a chloride, bromide, and in 
other combinations, silver is not uncommon, while a con- 
siderable percentage of the supply comes from gold, where 
it is frequently present in alloy to the amount of eight or 
ten per cent. 

The consideration of silver forms, therefore, a complex 
subject, and it might with propriety be discussed either with 
gold or together with lead, which shows how arbitrary is 
the economic classification starting with the metal as the 
primary basis for a division of this part of the subject of 
economic geology. This will become more apparent in the 

180 



SILVEK. 181 

later pages of the chapter, since this metal illustrates fully 
the fallacy of such a classification. Before the discovery 
of South America, the world's supply of silver came chiefly 
from argentiferous galena, and although many mines of 
true silver ores have been discovered in the two new conti- 
nents, it is still true that a large part of this metal comes 
from this source. A very few ounces of silver to the 
ton generally makes galena an ore capable of profitable 
extraction, in places where, owing either to difficulties of 
mining or lack of transportation facilities, it could not 
otherwise be mined. In many mines the lead just about 
pays the expense of extraction, and the silver thus won is 
profit. 

Silver Mines in the United States. — Practically all the 
silver of the country is produced in the Cordilleras, and, as 
will be seen by reference to the table of production at the 
close of the chapter, nearly all of this metal at present 
produced in the United States comes from the two states 
Colorado and Montana and the territory of Utah. A very 
few localities from this section are chosen for description, 
and these are the mines which are best known. 

Oomstock Lode. — Nevada has been, until within a few 
years, pre-eminently the silver-producing state of the Union, 
although, at present, it is fifth in rank of importance. 
Whereas, in 1877, the output of silver from this state was 
126,000,000, in 1891 it produced but 14,551,111. This 
decrease is due mainly to the abandonment of parts of 
the remarkable Comstock Lode, a mine which has never had 
a parallel in the history of mining. On the basis of the 
development of this mine a large city was founded, and 
a state literally created. With the abandonment of the 



182 ECONOMIC GEOLOGY OF THE UNITED STATES. 

lode the state has decreased in population and the region 
practically reverted to its original condition. 

The discovery and development of the Comstock Lode 
exerted a disturbing influence on the monetary world. 
Discovered in 1858, it was a wonderful producer until 1877, 
when it rapidly declined. The history of this mine has been 
so full of interest, and withal so remarkable, that a sum- 
marized statement of the more important events is given 
here. 1 It has been a history composed of a series of chapters 
of obstacles and of unusual difficulties which were some- 
times insurmountable. These began with the discovery of 
the vein, when, by a series of frauds, the lode changed 
hands and the titles became confused, giving the excuse 
for long-continued and disastrous litigation. When dis- 
covered, the region was an utter wilderness, occupied by 
savages ; there was no fuel at hand, no timber for supporting 
the roofs of the tunnels, wages were extraordinarily high, 
and there were practically no supplies and no available 
water. Eventually a water supply for Virginia City was 
obtained from a distance of twenty miles, at an expense 
of over $2,000,000. It was necessary to transport timber, 
supplies, and machinery across a long stretch of desert 
country, and the progress of development was thus very 
seriously retarded. 

When the mines were well under way, and prosperity 
seemed, at last, to be at hand, litigation began. Fires 
destroyed the valuable timber in the mines, but above all, 
reckless extravagance of management interfered with the 
normal development of the lode. Before the close of 1861 

1 Lord, Comstock Mines and Mining. Monograph U. S. Geol. Survey, 
Vol. IV., 1883. 



SILVER. 183 

stock companies were formed, with a capitalization of more 
than $ 60,000,000, but notwithstanding the wonderful output 
of the mine, the stockholders realized but little from their 
investment. During the year 1863 water was added to the 
other difficulties, and the mines were flooded as the result 
of a break in the clay wall. From this time on, there was 
maintained a constant battle with water, and this led, in 
1871, to the beginning of the famous Sutro tunnel, which 
was commenced with the intention of constructing a drain- 
age-way for the water in the lower part of the mines. This 
tunnel, which is 20,489 feet long, and was constructed at a 
cost of $2,000,000, was not finished until 1878, and it was 
then too late to be of service, since the mine was far below 
the level of the tunnel. 

During the construction of the tunnel, and in the lower 
parts of the mine, a novel difficulty was encountered. Here 
the heat became intense and almost unbearable. In the 
Sutro tunnel the temperature rose to 110°-114°, and even 
the slightest exertion was so exhausting that, although cold 
air was constantly blown from the surface, it was necessary 
to change the force of miners four times a day. In the 
mine at the 3000-foot level, water, at a temperature of 170°, 
poured in, and the lower workings had to be abandoned. 
Normally, the temperature of the earth increases as the depth 
is increased, but many mines have gone below the level 
reached by the Comstock without having experienced exces- 
sive temperatures. Here, therefore, some abnormal cause 
must be sought, and although it has been suggested that 
the heat is supplied by the decomposition of feldspar in the 
country rocks, the most probable explanation is the presence 
of some intruded igneous mass which has not yet had time 



184 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



to cool. Any mine may encounter a similar phenomenon, 
but it is hardly probable that many will. 

PRODUCTION OF GOLD AND SILVER FROM THE COMSTOCK 

LODE. 



Year. 


Gold. 


Silver. 


Total. 


1859 


$30,000 




$30,000 


1861 


2,450,000 


$1,050,000 


3,500,000 


1864 


6,400,000 


9,600,000 


16,000,000 


1869 


2,962,231 


4,443,347 


7,405,578 


1872 


4,894,560 


7,341,840 


12,236,400 


1873 


8,668,793 


13,003,187 


21,671,980 


1875 


10,330,209 


15,495,312 


25,825,521 


1877 


14,520,614 


21,780,922- 


36,301,536 


1878 


7,864,558 


11,796,836 


19,661,394 


1879 


2,801,394 


4,202,091 


7,003,485 


1881 


430,248 


645,372 


1,075,620 


1884 


1,261,314 


1,577,438 


2,838,752 


1886 


2,054,920 


1,681,298 


3,736,218 


1888 


3,169,209 


4,458,058 


7,627,267 


1890 


2,002,000 


3,087,000 


5,089,000 


1891 


1,200,000 


1,900,000 


3,100,000 



Another unique feature in the Comstock is the fact that 
the ore is distributed with marked irregularity, and if it 
were not of very high grade in a few places, it could never 
have been worked. Many companies have spent millions of 
dollars without raising any ore, but have explored barren 
rock with the aid of frequently levied assessments, always 
in the hope of finding a "bonanza." At other times rich 
pockets, which have produced wonderful results, have been 
encountered. In all the explorations in this lode it was esti- 
mated, a few years ago, that there were constructed over 150 
miles of tunnels. Among the several rich pockets found in 



SILVER. 



185 



the Comstock, the so-called Great Bonanza, which was dis- 
covered in 1873, was the most remarkable. The rock re- 
moved carried as high as $93 to $632 of gold and silver per 
ton, and from 1873-1878 $60,732,000 of these metals were 
produced from one mine alone. During the years 1875 
and 1876 this pocket produced over $16,000,000 a year, 
its influence being noticed in the table on page 184, which 
shows the output of the lode. From 1859 to 1890 the total 
product of the lode was fully $325,000,000. 

The Comstock Lode * is a belt of quartz about 10,000 feet 
long and several hundred feet broad, showing slight undula- 



5 vn„v 




M V ^ \/v V V 

\] >/ V v v vvv 



V v\ J >»*., 

"1 



,v , V ^ v v V, 



Fig. 18. — Cross-section of Comstock Lode, Nevada. B, diorite; Db, diabase; 
H, hornblende andesite; A, augite andesite; 8, Sutro tunnel; V, vein mat- 
ter ; Q, quartz. (After Becker.) 

tions and at each end branching and disappearing. It 
follows approximately the contact of two igneous rocks 
(Fig. 18), a diabase and a diorite, and dips east of south at 



1 The geology of this district is fully described and ably discussed by 
Becker, Geology of the Comstock Lode, Monograph, U. S. Geol. Survey, Vol. 
III., 1882. 



186 ECONOMIC GEOLOGY OF THE UNITED STATES. 

an angle of 33°-45°. There is abundant evidence of faulting 
by the presence in the vein, of horses, breccia, slickensides, 
etc., and this led Richtofen, who first studied the lode, to 
consider it a true fissure vein ; but more recent studies have 
shown that it is not entirely a fissure vein, but in part an 
ore channel following the contact of the two igneous rocks. 
The hanging wall is diabase, and the foot wall is diorite for 
about three-fourths of the distance, with slates for the 
remainder. 

As has been stated, the ore is extremely irregular in dis- 
tribution, occurring in bonanzas, sometimes of marvellous 
richness, occasionally carrying several thousand dollars to 
the ton, but only in spots assaying above the $ 15 to $20 to 
the ton, which is necessary to make the mine pay. It is 
found that near the diorite the ore is usually poorer, and 
that here the proportion of gold increases. The ore minerals 
are often so disseminated that they elude investigation, but 
they are probably argentite and native gold and silver. 

Some interesting results have been obtained from the 
careful studies of the lode with reference to its origin. 
The region is one of great geological complexity, meta- 
morphic rocks and granites being traversed by the follow- 
ing igneous rocks : diorites, quartz porphyry, two ages of 
diabase, two ages of hornblende andesite, augite andesite, 
and basalt. Analyses have shown that in the diabase and 
diorite the metallic elements found in the vein are present 
in disseminated condition ; and a study of the rocks has 
resulted in proving that the diabase is very much decayed 
and altered near the lode. Moreover, the decomposed 
diabase contains much less metal than the fresh rock, but 
the proportions of the two metals found in the vein are the 



SILYEE. 187 

same in the fresh diabase. Everything indicates that the 
vein has been very recently formed, that very little erosion 
has taken place since its formation, and that the source of 
the metalliferous solutions is not very deep seated, — a con- 
clusion which is supported by the presence of heat in the 
lower parts of the mine. Becker has, after a careful study of 
all the conditions, concluded that the history of the lode has 
been, first a faulting of the rocks, then the percolation of 
water through the diabase, producing an alteration of the 
minerals and causing the extraction of gold and silver, 
principally from the augite, and finally an uprush of heated 
waters accompanied by the deposition of quartz, silver, and 
gold. The variations in the amount and character of the ore 
are due, partly to the variations in supply, partly to the 
influence of the neighbouring rock. 

Eureka District. 1 — A second important silver-producing 
district in Nevada is the Eureka, in the eastern part of the 
state. This district was discovered in 1864, and active oper- 
ations begun in 1868. It is an argentiferous galena vein, 
and up to 1882 the output was not far from $60,000,000 of 
precious metals and 225,000 tons of lead. There are two 
mining areas, Prospect Hill and Ruby Hill, in which the 
mode of occurrence is very similar. The rocks, which are 
tilted Cambrian limestones and shales, are folded, and while 
the shales have bent without fracturing, the limestones have 
been crushed and brecciated. There are also distinct faults, 
some of which have a considerable displacement ; and crossing 
these stratified rocks are intrusions of quartz porphyry and 
rhyolite. In fissures, crevices, and caves in the crushed 

1 This district has served as the subject of a valuable memoir by Curtis, 
Monograph, Vol. VII., U. S. Geol. Survey, 1884. 



188 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



limestone, the argentiferous galena, with some gold, is 
irregularly distributed through a gangue of calcite and iron 
oxide (Fig. 19). Down to the water-line the ore is ox- 
idized to a silver-bearing carbonate and sulphate of lead. 
Both in richness and in distribution the ore is irregular, 




Fig. 19. — Cross-section of Eureka Consolidated Mine, Nevada. Figures refer to 
levels. Dotted portion, quartzite ; unshaded part, limestone ; small portion 
cross-lined, shale; ore, (0). (After Curtis.) 



there being many areas of lean ore and frequent rich pockets. 
Sometimes the galena carries from $100 to $150 of silver and 
from |1 to $10 of gold to the ton. 

Apparently, during the upheaval of the region, ore-bearing 
solutions entered the rock by the path of least resistance, 



SILVER. 189 

sometimes passing along faults, but most commonly entering 
the crevices between the crushed limestone. It was thought 
that possibly the limestone itself might have furnished the 
ore, but analyses have shown that the quartzite, shale, and 
limestone have only minute quantities of silver, and hence 
this seems improbable. The most probable source is the 
intruded rhyolite, from which the ore may have been derived 
either by solfataric action or by infiltration. In places 
chambers have been dissolved out and later partly filled, 
and in others there is evidence of a replacement of the 
limestone. 

Other Silver Mines of the United States. — While Nevada 
has been decreasing its output of silver, Colorado has, since 
1877, been rapidly increasing, and this state is now, as it has 
been for a number of years, the chief silver-producing state 
of the Union. There are in this state many mines, chiefly, 
though not entirely, of argentiferous galena, and, also, there 
are many modes of occurrence. The two most important 
mining districts in Colorado are at Leadville and Aspen, 1 
from both of which argentiferous galena is produced. The 
Molly Gibson mine of the Aspen district is at present 
producing native silver in a pink barite gangue, and the 
ore in places is nearly pure silver, the assays in some cases 
giving from 2000 to 12,000 ounces. Recently a mining 
camp at Creede has become important, and its output of 
5,000,000 ounces of silver, in 1892, is the reason for the 
increased output of the state in that year, in spite of the 
fact that parts of the Leadville vein had begun to decrease 
their output. The deposits are apparently fissure veins in 

1 The geology of the Aspen district is described by L. D. Siver in Engi- 
neering and Mining Journal, Vol. 45, 1888, pp. 195, 196, and 212. 



190 ECONOMIC GEOLOGY OF THE UNITED STATES. 

igneous rocks. The Leadville district, which is one of the 
most important mining districts in the country, is described 
in the chapter on lead, and may be considered to illustrate 
one of the modes of occurrence of silver. In Colorado 
nearly every mode of occurrence and nearly every ore of 
silver is found. 

In Montana, the state second in importance as a silver- 
producer, very nearly the same conditions exist; but here 
a considerable part of the supply is extracted from the 
copper at Butte. The veins of this region are altogether 
quite remarkable. There are two closely associated series 
of veins in one of which the predominating ore is copper, 
while in the other silver sulphides are common. Practically 
no copper occurs in the latter and the gangue is rhodonite, 
a silicate of manganese, although this metal is not found in 
the copper veins. Thus, although so closely associated, these 
veins are widely different in character, pointing to a deep- 
seated origin probably at different times. 

Utah has also increased its silver output. Nearly one-half 
of the supply of this territory comes from the mines at Park 
City in Summit County, although there are several other veins 
producing large amounts of silver. The ore is a silver lead 
ore, and, since the beginning of 1887, more than 3,000,000 
ounces of silver have been produced each year. The Ontario 
mine of this district is in a well-defined fissure traversing 
quartzite irregularly. A mass of porphyry occurs at no 
great distance, and in places actually forms the hanging 
wall. Below 400 feet the ore is undecomposed galena, 
blende, and copper sulphide rich in silver. There are also 
in this territory mines of chloride of silver. From Idaho, 
which is now the fourth state in order of importance as 



SILVER. 191 

a silver-producer, the greatest amount of ore is obtained 
from the Coeur d'Alene mine, 1 which has a low-grade argen- 
tiferous galena exposed in great quantities and easily mined. 
This district, which, in 1886, produced only 116,246 ounces 
of silver, in 1891 had an output of 1,825,765 ounces. 

Considerable silver is mined in Arizona, and here also 
much of it is from argentiferous galena. Of the several 
districts, that at Tombstone in Cachise County has attracted 
most attention. According to Phillips 2 the ore here is 
bedded chiefly in limestones, which are stratified with shales 
and quartzites, and the series is folded, faulted, and crossed 
by dikes of porphyry. The ore follows the bedding for a 
distance, then breaks across it nearly vertically, following 
either a crack or a fissure, and again becomes horizontal. A 
variety of ores occurs in the different mines, but, in general, 
in the limestone it is silver-bearing lead, although from 
some of the mines a chloride of silver and free gold are 
obtained. New Mexico has a number of silver occurrences ; 
but the production of this metal in the territory is not 
as great as it might be with better transportation facilities. 
There are remarkably few silver mines in California, and a 
large part of the output credited to that state is obtained as a 
by-product from the gold. This apparent poverty in silver 
mines in California is no doubt partly due to the fact that 
the energies and available capital of the state have entered 
into gold production; but it is chiefly due to the general 
absence of silver deposits in the Sierras and Coast Ranges 
of the state. 

1 The geology of this district is described by Professor J. E. Clayton in 
the Engineering and Mining Journal, Vol. 45, 1888, p. 108. 

2 Ore Deposits, pp. 536-541. 



192 ECONOMIC GEOLOGY OF THE UNITED STATES. 

These few districts, selected from many as the best known, 
illustrate the wide variety of occurrence of silver in this 
country ; and, when taken in connection with the description 
of foreign mines, and the silver-lead deposits, these will serve 
to indicate the manner in which silver occurs. There is no 
uniformity of occurrence, but the ore may be found in almost 
any position with relation to the surrounding rocks. Never- 
theless, one notices a striking uniformity of association with 
igneous rocks. 

As to distribution, practically all of the supply of 
silver in this country comes from the Rocky and Sierra 
Nevada mountains. Aside from here and the Black Hills, 
the only state which produces any considerable amount of 
this metal is Michigan, which, in 1891, had an output of 
less than $100,000. A few thousand dollars' worth of silver 
comes- annually from the southern Appalachian states, partly 
from the gold ores and partly from argentiferous galena. 
Throughout the belt of Archean metamorphic rocks numer- 
ous silver mines of this nature have been opened at various 
times, but they have rarely paid, since the veins are usually 
small and the percentage of silver low. Some of them, if 
situated in Europe, where the methods of mining are more 
economical and of reduction more saving, might be made 
to yield returns ; but, in this country, where labour is high 
and where we are accustomed to extravagant methods of 
mining and rapidly made fortunes, these deposits are not 
exploited. It is possible that in the future some of these 
may become profitable ; but while such immense returns are 
made from the western states this is not probable. 

The most striking features of the distribution of precious 
metals in this country is their remarkable development in 



SILVER. 193 

the west and their practical absence east of the Rockies 
and the Black Hills. The probable reasons for this are 
suggested in an earlier chapter. 1 There are no statistics 
at hand for the relative importance of the different ores 
of silver ; but it is evident that in this country an important 
part of the supply of this metal comes as a by-product 
from lead, zinc, copper, and gold mines. From these 
sources, by the advances in metallurgical methods, the 
production of silver is every year increasing. 

Mexico, Central America, and Canada. — Next to the 
United States, Mexico is the most important silver-pro- 
ducing country. There are, in this republic, many lodes 
which have been worked for a long period of time, many 
recently opened, and many which, owing to the condition 
of the country, have not been developed. One of the 
famous old veins is the ore channel of Guanajuata, the 
Vete Madre, which occurs at the unconformable contact 
between Devonian sla-tes and Triassic sandstones, and has 
a width of from 200 to 300 feet. The ore is principally 
argentite and native silver in a gangue of quartz and 
calcite. Another famous vein is the Vete Grande, in the 
state of Zacatecas, which is a true fissure vein with a 
width of about twenty-five feet. Both of these veins, 
although not worked to a great depth, are decreasing in 
quality, and consequently in output; but other veins are 
increasing, and new mines are being opened, so that the 
total output of the country does not decrease. The Mexi- 
can mines have usually a gangue of quartz or calcite, with 
either complex or simple sulphides for ores, many of 
them being argentiferous galena, weathered near the sur- 

i p. 95. 



194 ECONOMIC GEOLOGY OF THE UNITED STATES. 

face, to carbonates, etc. The mode of occurrence is very 
similar to that of this country, the silver-bearing belt being 
a southern continuation of our own Cordilleras. It is a 
wonderfully rich district in mineral products, but owing 
to the unstable condition of the nation, the cost of fuel and 
timber, and the difficulty of transporting machinery, it is 
only partially developed. 

From 1521 to 1875 Mexico produced 13,167,096,424 of 
silver, and since then its yearly output has steadily increased 
from about 121,000,000 to over 153,000,000 in 1891. This has 
increased the total output to date to nearly $4,000,000,000. 
Since the first production of silver in 1521, the annual sup- 
ply has increased steadily, with some minor fluctuations, 
and, as the prospects for the future seem equally bright, 
Mexico may yet take first rank in the production of this 
metal. 

Canada is a very small producer of silver,, the principal 
supply for many years having been obtained from a true 
fissure vein which crosses the schists, at Thunder Bay, on 
the shores of Lake Superior. Recently argentiferous veins 
have been discovered in western Canada, near Kootenay 
Lake, and this region promises to become an important 
silver-producing district in the future. Since the Cordil- 
leras extend into Canada, and are silver-bearing to the 
very boundary, there is every reason to expect its discovery 
when this region shall have been explored. 

Between South America and Mexico the countries of 
Central America have geological conditions so similar to 
the regions north and south of them that we may expect 
to find this an important silver-producing district when 
the political and social conditions become more advanced. 



SILVER. 195 

Already they produce some silver, the output in 1891 
having been about $2,000,000, but we know very little of 
the geology of these countries, and their mineral resources 
have never been tested. 

South American Silver Mines. — The western countries of 
South America, which are situated in a southern continua- 
tion of the same general region as that of our Cordilleras, 
shared with Mexico the highest rank, in the production of 
silver, before the developments of the last thirty years in the 
United States. At present, this general district holds third 
rank; and very nearly all of the output comes from the 
countries which are situated in the Andes. Of these, Bolivia 
is by far the most important. Here there are a number of 
large and very rich silver mines, but of these the best known 
is the Potosi, which is famous for its almost fabulous rich- 
ness. It was discovered in 1545, and worked continuously 
until 1809, and since then more or less continuously to 1850. 
From this mine over $1,000,000,000 worth of silver has been 
produced, the output at times having amounted to over 
$9,000,000 a year. The occurrence is apparently in a fissure, 
crossing quartz porphyry and slates, being less productive 
in the latter. Native silver, pyrargarite, and chloride of 
silver are the most common ores. During the time of 
greatest prosperity, this mine caused the development of a 
large city high up in the mountains ; x but now the mine is 
practically abandoned, although, after its long idleness, it is 
soon to be reopened. At present, the most important mining 
district in this country is the Huanchaca. Since 1545 the 

1 This town is one of the highest inhabited towns in the world, being at 
an elevation of 13,280 feet. In 1611 there were 160,000 inhabitants, although 
now not more than 10,000. 



196 ECONOMIC GEOLOGY OF THE UNITED STATES. 

average 1 yearly output of silver from Bolivia has never 
fallen below 11,700,000, and for a large part of the time the 
average has exceeded $5,000,000. Since 1876 the average 
annual output has exceeded 110,000,000, amounting, in 1891, 
to $15,488,000. 

Next in rank to Bolivia is Peru ; and in this country the 
most important silver mine is the Cerro de Pasco, which was 
discovered in 1630, and has been worked almost continuously 
since then. Although this mine has been exploited for 260 
years, and has probably produced fully $300,000,000, the 
shafts have not extended below 300 feet, and there is proba- 
bly a greater body of low-grade silver ore exposed in this 
mine than in any other partly developed vein in the world. 
In 1841 the output reached nearly $4,000,000 a year; and 
since 1788 the annual production has not fallen below 
$1,000,000 in any year, excepting when closed during the 
war of independence (1821-1825). The mine has never 
been systematically and scientifically developed, although 
recently explorations have been carried on in the interest of 
a syndicate ; but it seems probable that, on account of the 
difficulties of transportation and the low grade of the ore, 
it cannot be worked below the water-line. Even at the pres- 
ent time, the mine is worked by the natives, and the metal 
extracted by the crude Patio process ; and by these means 
1,000,000 ounces of silver are annually produced. Below the 
water-line the ore is a sulphide, and above this it is oxidized, 
occurring in an easily worked ferruginous earth. Since 1533 
Peru has had an annual average output exceeding $1,000,000, 
and usually exceeding $3,000,000, while during the first decade 
of this century the output exceeded $6,000,000 a year. 
1 The average being taken for periods of five and ten years. 



SILVER. 197 

The third most important silver-producing country in 
South America is Chili, and here also there are several 
very notable districts. A very peculiar deposit exists in the 
Chanarcillo district, 'where the silver is found in the form 
of a bromide and chloride, varying remarkably from rock to 
rock. It occurs in Jurassic limestone, associated with erup- 
tive diorites, and appears to be in part a contact, in part a 
fissure deposit. The descriptions of South American mines 
are so meagre, and often contradictory, that very little of 
value can be stated concerning their geological occurrence. 

Chili has not been an important silver-producing country 
for as long a time as Bolivia and Peru ; but since 1840 the 
product has annually exceeded 81,000,000, having rapidly 
increased until 1886, when the output was $8,727,600, and 
since then having rapidly decreased, until, in 1891, only 
about $3,000,000 were produced. The other countries of 
South America, excepting Colombia, produce practically no 
silver ; and in that country the supply comes largely from 
the gold product. 

Australasia. — This forms the fourth most important silver- 
producing district in the world. The supply comes in part 
from the gold ; but there are also mines of silver, with sul- 
phides for ores, and also argentiferous galena mines. None 
of the countries of this continental area, excepting New 
South Wales, are of importance in the production of this 
metal. Here, aside from the silver produced as a by-product 
in gold mining, the principal district is the Barrier range, 
where there is an argentiferous lead ore, which produced, in 
1892, 13,336,809 ounces of silver and 56,633 tons of lead. 

European Silver Mines. — Germany is the leading silver- 
producing country of Europe, and there the metal exists in 



198 ECONOMIC GEOLOGY OF THE UNITED STATES. 

very complex association. True silver mines occur in Silu- 
rian schists, in the Andreasberg district of the Harz Mountains, 
but generally the metal is obtained from the complex sul- 
phides. At Freiberg, in the Erzgebirge, the richest argen- 
tiferous galena occurs. Silver is also extracted from the 
complex sulphides, galena, blende, copper and iron pyrite, at 
Clausthal, in the Harz ; and it is found in the same general 
association in the Rammelsberg district, which is also in the 
Harz. In the latter district the veins are bedded and folded 
with Devonian slates, and in the other mining districts of 
Germany there are segregated and fissure veins frequently 
associated with eruptive rocks. Since 1820 Germany has had 
an average annual output of silver exceeding 11,000,000, 
and this has been gradually increasing, until, at present, over 
$7,000,000 are produced each year. 

In France considerable silver is annually produced, the 
ore being chiefly argentiferous galena occurring in schists 
and granites which are crossed by porphyry. Spain contains 
several silver-producing districts, most of which have argen- 
tiferous galena for an ore. The Guadalajara mines occur in 
gneiss and produce chiefly argentite and ruby silver, with 
some galena, in a gangue of barite and quartz. In Austria- 
Hungary the silver is found in very nearly the same modes 
of occurrence as in Germany, the ore being chiefly argen- 
tiferous galena and other complex sulphides. The two most 
important districts are Schemnitz and Kremnitz. Silver has 
been produced from the, Przibram district, in this region, 
since the year 843, and some of the mines have descended to 
a great depth. The occurrence in this country is usually in 
association with eruptive rocks. Since 1830 the average 
annual output of silver from Austria-Hungary has exceeded 



SILVER. 199 

11,000,000, and for the last fifteen years the average has been 
over 12,000,000. 

No other European countries produce more than $1,000,000 
worth of silver annually, but some is obtained in Russia, 
principally from the gold, and some in Sweden and Norway, 
where ores of native silver and of silver sulphides occur in 
metamorphic rocks which are crossed by igneous intrusions. 
In Great Britain a small amount of silver is extracted from 
the ores of copper and zinc in Devonshire and Cornwall, as 
well as from limestones in other parts of the islands, where 
it occurs in the form of argentiferous galena. The Cornwall 
and Devonshire mines are either in or near igneous rocks. 1 

Origin of Silver. — The remarks made above concerning 
the occurrence of silver in the United States apply with 
equal force to the foreign silver veins. In Europe, the metal 
is found most commonly in the complex sulphides, argen- 
tiferous galena, blende, copper pyrite, etc., but sometimes in 
simple sulphides or with other mineralizers. The same is 
true of Australia, but here galena is the principal source. 
The United States and Mexico illustrate the same associa- 
tions, but in these countries the simple ores of silver are more 
common, while in South America the larger proportion of 
the silver comes from ores unassociated with other metals. 
The greater part of the silver of the world is obtained as a 
by-product in the mining of other metals, and this is strik- 
ingly the case in Great Britain, Germany, and Austria-Hun- 
gary, where a great variety of metals come from the same 

1 Eor detailed descriptions of the mining districts of Europe, and par- 
ticularly of Great Britain, reference may be made to Phillips' Ore Deposits. 
Davies' Earthy and Other Minerals and Mining ; Metalliferous Minerals and 
Mining, Davies ; and von Groddeck's Die Lehre von dem Lagerstdtten der 
Erze also give good descriptions of European statistics. 



200 ECONOMIC GEOLOGY OF THE UNITED STATES. 

mine ; but no single mineralogical association of silver is so 
common as that with the sulphide of lead. Next in impor- 
tance are the simple ores of silver, of which the sulphides are 
the most abundant, although chlorides and oxides are not 
rare. A third important source is from gold, with which it 
is alloyed. Native silver is found, but it is not common ex- 
cept in its alloy with gold. It is a striking fact that the 
source of a great part of the silver is such that, at its present 
price, it could not be profitably extracted if the metals with 
which it is associated were of no value. 

For the mode of occurrence no general statements can be 
made. Perhaps true fissure veins are the most important, 
although veins of segregation, bedded veins, contact, cham- 
ber, replacement, and other modes of occurrence are not 
uncommon. Silver is not found in placer deposits, for the 
reason that it is chemically weak, and, under the influence 
of weathering, loses its metallic character, disintegrates, and 
is carried away with the lighter and finer particles. The 
original source of silver is undoubtedly igneous rocks, where 
it occurs in association with the metalliferous bisilicates, 
chiefly augite, hornblende, and mica. Consequently this ore 
is found most commonly near its source ; that is, in associa- 
tion with igneous rocks which have been subjected to altera- 
tion by the percolation of water charged with substances 
which give to it a solvent power. But since sedimentary 
and many metamorphic strata are derived, either directly or 
indirectly, from igneous rocks (even if it is necessary to 
trace them back to the original crust of the earth) , it is not 
unnatural to expect to find that such deposits have at 
times been derived from these secondary sources. Analyses 
have demonstrated the existence of silver in many sedi- 



SILVER. 201 

mentary rocks, but rarely in sufficient abundance to become 
concentrated, excepting under very favourable circumstances. 
This is what would be expected, since silver is a compara- 
tively rare element, and, in the formation of sedimentary strata, 
would tend to become even more disseminated than in the 
original igneous masses. Even where found in sedimentary 
rocks, unless unquestionably bedded or segregated, the source 
may have been some deeper lying beds of igneous rocks. 
Silver is found, both in this and other countries, in moun- 
tainous regions, chiefly those of recent date, because here 
there are cavities for its deposition and abundant igneous 
rocks for a source of supply. 

Uses of Silver. — Silver is extensively used in the arts, 
in jewelry, and in utensils, chiefly in tableware and show 
utensils. Its brightness and beautiful white colour make 
it valuable for these purposes, although its habit of tarnish- 
ing, when in the presence of sulphurous gases, detracts 
from its value. There are also numerous alloys of silver, 
the most important being an alloy of gold and silver, and 
copper and silver, the last two metals being added to coin- 
age, and other gold, either singly or more rarely together, for 
the purpose of increasing its hardness. Coinage silver is 
alloyed with copper. By alloys of other metals crude imita- 
tions of silver are made. Such are the alloys of tin, nickel, 
and bismuth, of copper, nickel, tungsten, and aluminum, and 
of copper, nickel, zinc, and cadmium, etc., the latter bearing 
a closer resemblance to silver than the others. 

Coinage has been an important use of the metal, but prom- 
ises to become more and more unimportant. When, in 1873, 
the Latin Union and Germany and Holland ceased the free 
coinage of silver, this metal became a commodity, and since 



202 ECONOMIC GEOLOGY OF THE UNITED STATES. 

then it has been subjected to the fluctuations in price which 
result from variations in supply and demand and the manipu- 
lation of syndicates ; and this is probably the future fate of 
silver to even a more marked degree. From 1687 to the close 
of 1873 the ratio of silver to gold was remarkably uniform, 
having never fallen below 14.14, and in only two years hav- 
ing risen above 16.00. The general tendency, however, was 
toward a greater ratio of silver, or, what is the same thing, 
a smaller relative value. In 1687 the ratio was 14.94; in 
1873 15.92 ; but since the latter year the ratio has steadily 
increased, until, in 1892, it reached 23.73, and is still (1893) 
increasing at a startling rate. Since 1859 the price of silver 
has decreased from $1,360 to $0,876 per ounce in 1892, with 
the price rapidly falling. This is due, not entirely to the 
suspension of free coinage, but, partly, to the increase in 
output. This increase began in 1860, but the price did not 
begin to fall rapidly until 1874. The coining value of silver 
in the United States is $1.2929 per ounce, which is a highly 
artificial value. 

If all the important nations of the world could agree upon 
a uniform ratio between gold and silver, the latter might still 
be safely coined; but such an agreement seems unlikely to 
be reached, and it is doubtful if, in the future, silver will be 
extensively used for coinage, excepting for small denomina- 
tions. The future of the silver industry is therefore far 
from bright, and it will not be surprising if we should wit- 
ness in the next few years a startling decrease in production. 
This metal has been given an unnatural position which it 
does not deserve. Grant it a permanent or moderately 
permanent value, something like its value in the middle of 
the last decade, and the output will continue to increase 



SILVER. 203 

even more rapidly than it has in the past ; and there seems 
to be no moderate limit to the ultimate output. This metal, 
although truly a precious metal, and by no means common, 
is far too common for use as a standard of coinage, and 
its continued use for this purpose means a progressively 
increasing production which will call for a frequent re- 
establishment of the ratio. The nations which have not 
yet discovered this fact are liable to suffer for their short- 
ness of vision. 1 

For a verification of these remarks a comparative reference 
needs only to be made between the increase in output of 
gold and silver in the world during the past fifteen years. 
Between the years 1875 and 1891 the amount of silver annu- 
ally produced in the world has increased from $82,000,000 
to 8185,599,600, while the increase in gold production has 
been from $111,000,000 to $125,299,700. These are startling 
and very significant figures when we consider the probability 
of a corresponding rate of increase for many years, provided 
free coinage is established without a marked increase in de- 
mand. In this country the relative increase in production 
of the two metals is even more striking ; for, in 1850, 1 part 

1 While this has been in the hands of the publishers, a long-continued 
and very varied discussion of the silver question has been in progress. All 
sides of the question have been considered, and finally the country has 
receded from its unfortunate position as a buyer of silver at an extremely 
artificial price. Much pressure has been brought to bear to prevent the 
repeal of the silver law, and much hardship has resulted in the mining dis- 
tricts. This has been, in part, at least, caused by the silver miners, who 
have in many cases closed mines which could readily be made to yield profit 
at a much lower price for silver than that now existing. The industry is 
very much depressed as the result of this interference with the unnatural 
stimulation of the past few years. A more healthful condition will, how- 
ever, eventually follow this change, and the silver industry will become a 
more permanent and business-like industry. 



204 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



of gold was produced to 0.016 of silver, and, in 1889, the 
product ratio was 1 of gold to 32.32 of silver. 

The amount of silver coined in the United States from 
1793 to 1824 exceeded $1,000,000 in only two years. From 
that time to 1874 the coinage of silver fluctuated greatly, 
at one time (1853) reaching over 19,000,000, and in 1864 
falling to a little over a half million, while, in several 
other years the coinage fell below $1,000,000. Since 1874 
the coinage of silver has averaged nearly $30,000,000 a year, 
and in 1890 reached $39,202,908. During the year 1891 the 
silver coinage of the principal nations using this metal was 
as follows : India, $32,670,498 ; United States, $27,518,857 ; 
Mexico, $24,493,071 ; Spain, $11,251,000 ; Japan, $8,523,904; 
Portugal, $7,277,040 ; Great Britain, $5,141,594. No other 
nation issued more than $4,000,000 of silver. 

Production of Silver. — The following tables show the value 
of the production of silver, in the United States and the 
world, based upon the United States coinage value, $1.2929 
per ounce. 

PRODUCTION OF SILVER IN THE UNITED STATES. 



States. 


1877. 


1880. 


1885. 


1888. 


1890. 


1891. 


Colorado . . 


$4,500,000 


$17,000,000 


$15,800,000 


$19,000,000 


$24,307,070 


$27,358,384 


Montana . . 


750,000 


2,500,000 


10,060,000 


17,000,000 


20,363,636 


21,139,394 


Utah. . . . 


5,075,000 


4,740,000 


6,750,000 


7,000,000 


10,343,434 


11,313,131 


Idaho . . . 


250,000 


450,000 


3,500,000 


3,000,000 


4,783,838 


5,216,970 


Nevada . . . 


26,000,000 


10,900,000 


6,000,000 


7,000,000 


5,753,535 


4,551,111 


Arizona . . . 


500,000 


2,000,000 


3,800,000 


3,000,000 


1,292,929 


1,913,535 


New Mexico . 


500,000 


425,000 


3,000,000 


1,200,000 


1,680,808 


1,713,131 


California . . 


1,000,000 


1,100,000 


2,500,000 


1,400,000 


1,163,636 


969,697 



SILVER. 205 

Nearly one-half of this product comes from silver-lead ore. 
Over one-third of the total amount of silver produced in 
the United States comes from Colorado, nearly two-thirds 
from Colorado and Montana, and practically all from, or 
west of, the Rockies. In 1891 the only other states pro- 
ducing over $100,000 of silver, and all of these less than 
$500,000, are, in the order of their rank, Texas, Oregon, 
Washington, and South Dakota. 

Colorado increased its output at a remarkable rate from 
1877 to 1880, owing to the development of the Leadville 
mines, and since then the production has steadily increased. 
In 1880 this state took the lead from Nevada, and this 
it has maintained each year, with the exception of 1887, 
when Montana produced a little more than Colorado. The 
output of silver from Montana has increased rapidly, and 
both Utah and Idaho have slowly increased. Nevada, on 
the other hand, has decreased its output very greatly, chiefly 
because of the abandonment of the Comstock Lode. 

SILVER PRODUCTION OF THE UNITED STATES. 

1857 $50,000 

1861 2,000,000 

1864 11,000,000 

1869 12,000,000 

1871 23,000,000 

1874 37,300,000 

1880 39,200,000 

1885 51,600,000 

1890 70,465,000 

1891 75,416,500 

1892 83,909,210 



206 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



There has been a steady and very rapid increase, with 
some fluctuations, since 1861. From 1880 to 1892, inclusive, 
a period of thirteen years, there has been an average annual 
increase of nearly 13,440,000, and, in the last few years, 
a much greater rate of increase. 



PRODUCTION OF SILVER IN THE WORLD. 



Countries. 


1880. 


1885. 


1888. 


1890. 


1891. 


United States . . 


$39,200,000 


$51,600,000 


$59,195,000 


$70,465,000 


$75,416,500 


Mexico . . . . 


25,167,763 


32,112,000 


41,373,000 


50,356,000 


53,000,000 


Bolivia .... 


11,000,000 


10,000,000 


9,578,000 


12,514,200 


15,4S8,000 


Australasia . . 


227,125 


1,048,000 


5,000,000 


10,731,300 


12,929,300 


Germany . . . 


5,576,699 


1,021,000 


1,332,022 


7,567,500 


7,480,800 


Peru 




1,988,000 


3,128,000 


2,734,300 


3,112,000 


Chili 


5,081,747 


8,727,600 


7,723,957 


5,140,800 


3,000,000 


France .... 




2,120,000 


2,053,000 


2,955,600 


2,955,600 


Spain. .... 


3,096,220 


2,258,000 


2,140,400 


2,140,400 


2,140,400 


Austria-Hungary 


1,994,880 


2,192,200 


2,166,440 


2,103,500 


2,103,500 


Central America 






2,000,000 


2,000,000 


2,000,000 


Japan .... 


916,400 


960,000 




1,765,000 


1,798,800 


Columbia . . . 


1,000,000 


400,000 


1,000,000 


830,000 


1,298,000 


Total for World 


$96,700,000 


$118,095,150 


$140,706,413 


$173,743,000 


$185,599,600 



The United States, in 1891, produced 40.6 per cent of 
the silver of the world; Mexico 28.5 per cent, and these 
two countries together 69.1 per cent of the world's supply. 
The United States, Mexico, Bolivia, and Australasia pro- 
duced 84.5 per cent of the silver, and over three-fourths of 
the supply of the world came from the western hemisphere. 
In the above table the most striking facts are the steady 
increase of output from the important silver-producing 
countries and the remarkably rapid rate of increase in the 
case of the United States, Mexico, and Australasia. 



SILVER. 207 

SILVER PRODUCTION OF THE WORLD. 

1849 $39,000,000 

1860 40,800,000 

1865 52,000,000 

1870 64,000,000 

1875 82,000,000 

1880 96,700,000 

1885 118,095,150 

1890 173,743,000 

1891 185,599,600 

Between the years 1860-1891 inclusive, thirty-one years, 
the increase in production of silver has been at the rate 
of nearly $4,700,000 a year. From 1872 to the close of 
1891, twenty years, the annual rate of increase has exceeded 
$5,700,000, and within the past few years this rate has been 
much greater, and at present is more than double the latter 
amount. 



CHAPTER IX. 

COPPEB. 

General Statement. — Copper, like silver, varies widely in 
mineralogical association and mode of occurrence. The ores 
most commonly found are, native copper, the sulphide 
chalcocite, the sulphides of copper and iron bornite and 
chalcopyrite, the oxides cuprite and melaconite, the silicate 
chrysocolla, and the carbonates azurite and malachite. 
Other ores are more rarely found, but the most important 
sources of copper are the sulphides and native copper, the 
other minerals being usually the result of oxidation above 
the water-line. Almost every mode of occurrence is illus- 
trated by mines of this metal, and usually other metals are 
found in association with the copper. This is very markedly 
true in England, Germany, and Austria, where, from the 
same mine, gold, silver, copper, lead, zinc, and other metals 
are extracted. Indeed, aside from the mechanical associa- 
tion of the ores of these metals, the sulphides of copper 
are usually complex, and, by metallurgical processes, both 
gold and silver are frequently obtained from them. A not 
inconsiderable percentage of the supply of these two metals 
comes from this source, and, where the ores of copper are 
argentiferous or auriferous, the mining and extraction of 
copper is sometimes rendered profitable in places where, 
without the presence of precious metals, this would not be 
possible. 

208 



COPPER. 209 

A very few countries supply the copper of the world, 
and if it were not for the mines of the United States, 
Spain, and Chili, the product of the world would be very 
limited. In the United States, which is far ahead of other 
nations in the production of this metal, as well as in that 
of silver and gold, the distribution of the ore is very local. 
Only three districts, Montana, Michigan, and Arizona, are 
of particular importance as copper-producers ; and of these, 
the first two produce by far the greater amount. In these 
two states the copper comes from two exceedingly small areas. 

Appalachian States. — From the eastern and southern 
states only a few hundred tons (in 1892, 580 tons) are 
annually produced. There are, however, in this belt, chiefly 
in the metamorphic rocks, considerable stores of medium 
and low grade copper pyrite which have, in the past, given 
to the states of this region an importance in the produc- 
tion of copper far greater than they now possess. The 
development of the copper mines of the west caused these 
to be discontinued, because of the fall in price of the 
metal; but now that the demand for copper continues to 
increase, and new methods of cheap mining and extrac- 
tion have been perfected, the future of this district seems 
brighter. In several of these states small copper mines 
are being exploited, but Vermont is the most important 
of them all. Here from the Copperfield mine 1,200,000 
pounds were produced in 1892. The copper mines of the 
belt of metamorphic rocks are, in some cases, in segrega- 
tion veins ; in others, in fissure veins ; and of the former 
class there are many veins which are either too small or 
too uncertain for exploitation, while others are merely 
copper-bearing iron pyrite veins. With the conditions 



210 ECONOMIC GEOLOGY OF THE UNITED STATES. 

existing in Germany and Austria, this district would 
assume considerable importance in the production of 
copper and other metals. 

Lake Superior District. — In copper, as in iron production, 
Michigan assumes importance, and in the case of both of 
these metals, the productive area is the belt of older rocks 
on the peninsula between Lake Superior and Michigan. 
This district, though now of second rank in this country, 
has, since its opening, produced more copper than any 
other in the world. Already the largest of the mines, the 
Calumet and Hecla, has extended to a depth greater than 
4000 feet below the surface, and there appears to be no 
sign of a decrease in supply. There are here a number 
of mines, great and small, some of them producing only a 
few thousand pounds of copper a year, but nine of which 
annually produce more than a million pounds, while the 
greatest, the Calumet and Hecla, had an output in 1891 
of more than 63,000,000 pounds. A number of the smaller 
mines have recently ceased operations, but the larger ones 
either maintain or increase their output from year to year. 
If necessary, the production of this district could be vastly 
increased for some time to come. 

The mines of the Keweenaw Point district were first 
discovered in 1845, although for centuries before this the 
Indians had made use of the boulders of copper for imple- 
ments and ornaments. Since 1845 the output from the 
Lake Superior region has steadily increased, with some 
minor fluctuations of recent date. In some of the mines, 
mineralized ores of copper are the source of the metal, but 
the most common ore is native copper frequently associated 
with native silver. 



COPPER. 211 

A series of interstratified sandstones, conglomerates, and 
diabases, of Algonkian age, form the rocks of the region, 
and these are tilted at an angle varying from 30° to 60°. 
The diabases are usually very much altered, and are classed 
as melaphyres; and that they are actual lava flows buried 
beneath later sediments is shown by a study of their 
field relations, and by the fact that many of them are 
amygdaloidal. 1 Copper occurs in these rocks in several 
conditions. The most important source of the metal is 
from the sandstones and conglomerates where it occurs as a 
cement, in grains, ramifying masses, and bunches sometimes 
weighing many tons. Usually the native copper ramifies 
through the rock, in the interstices between the pebbles 
and grains of sand, cementing them together, and frequently 
entering the crevices in the pebbles themselves. For the 
extraction of the metal the rock is crushed and then sepa- 
rated by concentrators. Strange though it may seem, the large 
masses of copper, which are too heavy for removal, are usually 
of little value, since they cannot be picked, nor blasted, nor 
cut excepting with great difficulty by means of chisels. 

A second source of copper is from the trap or melaphyre, 
where it is found, also in a native state, as a partial or com- 
plete filling of the amygdaloidal cavities, usually in associ- 
ation with calcite, quartz, native silver, and numerous other 
minerals. Native copper also occurs at the contact of the 
diabase flows, in veins of secondary minerals, chiefly epidote, 
and also in true fissure veins with calcite and quartz gangue. 
Here the influence of the country rock is well shown by 

1 An amygdule is a cavity in an igneous rock caused by the expansion 
of gas, usually aqueous vapour, and either partly or completely filled by the 
percolation of water at some subsequent time with a foreign mineral. 



212 ECONOMIC GEOLOGY OF THE UNITED STATES. 

the fact that these latter veins are frequently unproductive 
in the sandstone and conglomerate, although often rich in 
both silver and copper in the trap. 

The origin of this remarkable deposit has been variously 
accounted for by the different students of the geology of that 
region. That it is not a true contact deposit is shown by the 
fact that the amygdules in the diabase, the fissure veins, and 
the crevices in the broken pebbles are filled with copper, 
showing a subsequent deposition. In the igneous rocks 
copper is, next to iron, the most common of the metals 
which are used extensively in the arts ; and in none of these 
rocks is it more common than in diabase. A long-continued 
process of alteration has been passed through by the diabase, 
and the result is that many of the original minerals have 
been entirely changed in character. Probably, during this 
change the metallic constituents, together with quartz and 
calcite, were removed from the diabase and deposited in 
their present position. 

Whether by the decay of the heavy bisilicates, native 
copper was originally set free, or whether it was in the 
form of a sulphide in the rock, is a question which may not 
unreasonably be answered by assuming that both conditions 
were present, since diabases contain free sulphides of copper 
and also copper associated with the bisilicates. In order 
to explain the supposed alteration from copper pyrite to 
native copper, electro-chemical changes have been suggested, 
and this is a very reasonable hypothesis. The occurrence 
here is analogous to what is happening in many rocks, 
excepting that, in this case, we are dealing with copper 
instead of some more abundant substance. There are few 
more common phenomena in geology than the cementing 



COPPER. 



213 



of sandstones and conglomerates by oxide of iron, calcite, or 
quartz ; and amygdaloidal cavities filled with these or other 
minerals are present in all porous lavas which have been 
buried for a sufficient length of time to come under the 
influence of percolating waters. 

From 1847, when Michigan produced 213 tons 1 and the 
entire country 300 tons, to 1881, when Michigan produced 
24,132 tons of the total output of 32,000 for the coun- 
try, this state was the great copper-producer of the Union. 
Since 1853 the output has exceeded 1000 tons, and has 
gradually and steadily increased, and since 1870 more 
than one-half of this supply came from a single mine, the 
Calumet and Hecla. Next to this. mine the Tamarack and 
the Quincy are the most important in the district. The 
following table shows the increase in development of this 
region as a whole, and of these three mines, since 1860. 
Neither of these two mines produced copper in 1855, and the 
output of the district in that year was only 5,932,170 pounds. 

PRODUCTION OF COPPER IN THE LAKE SUPERIOR DISTRICT. 

Pounds. 





Calumet 

and 
Hecla. 


Tamarack. 


Quincy. 


Total 
Lake Superior 

Mines. 


1860 






1,940,414 


12,301,538 


1870 


14,061,584 




2,572,980 


24,290,231 


1875 


21,473,954 




2,892,617 


36,097,898 


1880 


31,675,239 




3,696,263 


49,615,811 


1885 


47,247,990 


181,669 


5,848,530 


72,759,082 


1890 


59,868,706 


10,106,741 


8,064,253 


100,695,359 


1891 


63,586,620 


16,161,312 


10,542,519 


114,328,218 


1892 


57,925,000 


16,426,683 


11,103,926 


107,540,304 



1 Long tons of 2240 pounds are used for the United States. 



214 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Montana Mines. — Twelve years ago Montana produced 
practically no copper, whereas now this state is far ahead of 
all others in the production of this metal. Very nearly the 
entire output of the state comes from a hill in the town of 
Butte, which is now the largest mining camp in the world. 
In this district there are a large number of claims, but few 
important mines. The ores are copper sulphide and chal- 
copyrite, with some blende and galena, in a gangue of quartz. 
Nearly all of these ores carry silver. The hill at Butte is a 
granite knob, crossed by rhyolite dikes which are a possible 
source of the copper. A series of nearly parallel veins 
cross the granite in fissures which extend beyond the limits 
of the hill. There is a considerable variation in the char- 
acter of the ore in different veins, and even in the same 
vein; but, although the Anaconda mine has reached a 
depth of considerably more than 1000 feet, there are no 
signs of exhaustion. The walls of the veins are not dis- 
tinct, but they have been partly replaced, and the veins 
enlarged by impregnation deposits. 

Notwithstanding numerous accidents, these mines have 
increased their output at a remarkable rate, and at present 
they produce more ore than any other copper district in 
the world. They are now producing fully 3000 tons daily, 
and it is claimed that the output can be easily made to reach 
175,000,000 pounds a year. The following table shows the 
wonderful development of the copper industry in Montana 
since 1882: — 



COPPER. 215 

PRODUCTION OF COPPER IN MONTANA. 

1882 9,058,284 lbs. 

1883 24,664,346 » 

1884 43,098,054 " 

1885 67,797,864 " 

1886 57,611,621 « 

1887 78,699,677 " 

1888 ...... 97,897,968 " 

1889 ...... 98,222,444 " 

1890 112,980,896 " 

1891 113,200,000 " 

1892 164,300,000 " 

Thus, in 1892, the output was increased over 51,000,000 
pounds, chiefly as the result of an increase in activity in the 
Anaconda mine. 

Arizona and other Western Mines. — Arizona has for many 
years been an important copper-producing territory, having, 
in 1882, held second rank, and since then third rank, in the 
country. Almost all of the ores at present mined are oxi- 
dized; and although there are great stores of copper here, 
the mines are not being rapidly developed, and the output 
is not increasing at a rate comparable with that of the two 
leading copper-producing states. There are several districts, 
and in all, so far as is known to the author, they are asso- 
ciated with eruptive rocks. We have not, however, as com- 
plete descriptions of these mines as of the two just described. 
As instances of the modes of occurrence of copper in Ari- 
zona, mention may be made of three mines : the Coronado, 
where the ore occurs in a dike of quartz porphyry crossing 
granite ; the Longfellow mine, in the Clifton district, in 
which the ore occurs in veins near the contact of felsite and 



216 ECONOMIC GEOLOGY OF THE UNITED STATES. 

limestone ; and the Black copper mine of the Globe district, 
where the ore is found in stockwerks, in gneiss, near a mass 
of diorite. The most important copper mines of the terri- 
tory are the Copper Queen, United Yerde, Old Dominion, 
and the Arizona Copper ; but there are numerous other mines 
of less importance. 

Colorado, which is next in order of importance, has no 
large copper mines, but a number of small deposits are be- 
ing worked, and considerable is supplied from the mines 
of other metals, notably from the Leadville lode, which is 
becoming richer in copper and poorer in other metals as the 
depth increases. The output from this state has shown a 
considerable increase in the last ten years. In California 
very nearly the same conditions occur ; but, owing to a fire 
in the principal mine, there was a slight decrease in output 
in 1891. More than one-half of the copper of Utah comes 
from a single mine, and the remainder chiefly from copper- 
bearing argentiferous galena. Valuable deposits exist in 
New Mexico, but the output of this territory has, so far, 
been very slight. 

Foreign Copper Mines. — The copper district of Spain and 
Portugal is next in importance to the United States. A 
copper-bearing series extends from near Seville across the 
Portuguese line to the Mason and Barry mine. The mines 
are situated in a zone of nearly vertical clay slates, with quartz 
porphyry dikes near by and nearly parallel to the veins. 
Being lenticular and parallel to the cleavage of the slate, 
the veins appear to be of segregation origin ; but whether 
the ore has been derived from the slate or the igneous rock 
has not been determined. Chalcopyrite, usually argentifer- 
ous, is the principal ore, but the black sulphide of copper is 



COPPER. 217 

also present. These veins were worked by the Romans, and 
the timbers used by them in their irregular galleries are 
admirably preserved by the presence of the salts of copper. 
From the very earliest times these mines have been worked 
as pits as well as true mines, and this is still the case. The 
Rio Tinto mine is by far the most important, and this at 
present has large quantities of copper in sight; but the 
Tharsis in Spain and the Mason and Barry mines across the 
Portuguese line are both very productive. Spain promises to 
keep the lead as a copper-producing country among Euro- 
pean nations for a long period. 

Chili has an output of copper of greater value than that 
of any other mineral product, but the industry is declin- 
ing. In 1855 this country produced one-half of the copper 
of the world, but to-day it produces less than one-tenth, 
this result being in large measure due to the increased pro- 
duction of other nations. There is, however, a noticeable 
decrease in the output of copper from Chili, and this is 
due in part to the decrease in richness of the ore in the 
lower tunnels of the mines and the increase in cost of mining 
at these depths, and partly to the unscientific methods of 
reduction by which the gold and silver contents are lost. 
The ores are copper pyrite below the water line and carbon- 
ates, silicates, etc., nearer the surface. Here, as in nearly 
all copper mines, there is an association with igneous rocks ; 
in the Rosario mine with diorite, in the Panulcillo as an 
apparent contact vein between mica schist and porphyry, 
and in the Carrizal Alto a vein frequently crossed by dikes 
and increasing in richness near these intersections. Other 
South American countries are not important as copper-pro- 
ducers. Venezuela ranks next to Chili, the principal mine 



218 ECONOMIC GEOLOGY OF THE UNITED STATES. 

there being the Aroa. Neither Bolivia nor Peru have as- 
sumed any considerable importance in this industry, although 
in both countries there are extensive deposits, at present 
inaccessible because of lack of transportation facilities. 

In Japan copper has been produced for over twelve cen- 
turies, and at present this country is the fourth most impor- 
tant. For 250 years the output of these mines has averaged 
nearly 3000 tons annually. Of the Japanese mines, the Ashio 
vein is by far the most valuable. The ore is black copper 
occurring in a fissure vein associated with eruptive rocks. 
Other Asiatic countries are not important copper-producers. 

Next in importance to Japan is Germany, which is second 
in rank among European countries. A small portion of 
the output comes from the various silver lead mines, such as 
Clausthal, the Freiberg mines, etc. In the Andraesberg dis- 
trict, 1 copper is obtained from veins in clay slate of Silurian 
age near a granite mass. But nearly ninety per cent of the 
German copper comes from Mansfield, at the southeastern 
end of the Harz. Here a series of folded sandstones, con- 
glomerates, gypsum beds, and bituminous marls occur, the 
latter being copper-bearing, and resting upon the sandstones 
and conglomerates as a bedded deposit. The copper-bearing 
shale in this marl contains from two to five per cent of 
copper in the form of grains of silver-bearing copper pyrite. 
Other ores are found, but not in abundance, and the copper 
itself, although occurring throughout the shale, is present in 
workable quantities in only a few bands. This very inter- 
esting deposit is rendered unworkable at the lower depths 
because of the influx of salt water from a salt lake, the Sal- 
ziger See, from which water enters the mine faster than it 
can be pumped out. The future of the mine is seriously 



COPPER. 219 

threatened by this difficulty, and the only possible relief is 
to drain the lake. 

Russia ranks next to Germany among European nations 
as a copper-producing country. There are .several districts, 
one in the Permian and Triassic strata on the western slope 
of the Urals, and another in the district of Nijne-Taguilsk in 
metamorphic schists not far from a mass of diorite. From 
both of these districts malachite and azurite are obtained 
in masses of sufficient size for ornamental work. This is 
particularly true of the latter region, which supplies the 
greater part of these minerals. That they are merely oxi- 
dized ores is proved by the fact that they pass into sulphides 
as the depth of the mines increases. 

Copper, in the form of copper pyrite, is found in Italy 
in chlorite schists associated with granites, and also in 
other districts usually in association with igneous rocks. 
Some of these mines were worked by the Etruscans. In 
Norway and Sweden this metal, chiefly in the form of pyrite, 
occurs in the metamorphic rocks. The Stora Kopparberget 
mine of Sweden has been worked since 1228 and perhaps 
earlier, and, although at the present only 271 tons are annu- 
ally produced, this mine had an output in the seventeenth 
century varying between 2000 and 3000 tons. In Aus- 
tria the copper is mined chiefly as an accessory in the silver 
lead mines, and the output is exceedingly small. The same 
is true of England, which every year becomes less important 
as a copper district, the chief supply coming from Devon- 
shire and Cornwall. 

The various colonies of Australasia produce copper, and 
the output of these countries combined give to this general 
area a rank next to Germany. Africa also produces some 



220 ECONOMIC GEOLOGY OF THE UNITED STATES. 

copper, the most important district being Cape Colony. 
Mexico, next to Australasia in importance, has produced 
very little from mines other than the Boleo mine of Lower 
California, where there is a very large deposit, which is 
profitably worked even with the difficulty of obtaining labour 
in that sparsely settled peninsula. Canada has copper mines 
in the metamorphic rocks of the province of Quebec, in Nova 
Scotia, and elsewhere, and recently important discoveries 
have been announced in British Columbia. The Algoma 
nickel mines are important sources of Canadian copper. 
From the metamorphic rocks of Tilt Cove, Little Bay, and 
elsewhere in Newfoundland, copper pyrite has been produced 
in considerable quantities. Recently the industry has rapidly 
declined, and at present some of the most important mines 
are closed. There are other valuable deposits in different 
parts' of the island, but the poverty of the colonists, the 
inaccessibility of the region, and the existence of certain 
fishing privileges which the French hold, have interfered 
with their development. 

Occurrence and Origin of Copper. — The distribution of cop- 
per deposits is extremely widespread, but the greater part 
of the world's supply comes from a very few localities. 
Excluding the mines at Keweenaw Point (Michigan), Butte 
(Montana), one or two mines in Chili, the Ashio mine of 
Japan, the Rio Tinto series in the Spain-Portugal region, 
and the Mansfield mines of Germany, and the copper product 
of the world is extremely slight. Yet these important areas 
cover only a few hundred square miles. Africa, outside of 
Cape Colony, Asia, exclusive of Japan, and South America, 
with the exception of Chili, are practically non-producers of 
copper. But in all of these regions copper is found, and if 



COPPER. 221 

the demand continues to increase, and facilities for trans- 
portation are introduced, some of these will be developed, 
particularly if, as seems possible, the present extravagant 
production of the large mines of this country continues until 
they are exhausted. The American mines have had a dis- 
turbing influence on the copper market of the world, and 
have made copper mining impossible in some districts ; but, 
on the other hand, they have been the means of introducing 
new and more economical methods of extraction, and, at the 
same time, by reducing the price, have aided in the introduc- 
tion of copper into new fields. 

It will be noticed, in the above description of the copper 
occurrences of the world, that the Lake Superior mines are 
practically unique in the fact that they are deposits of native 
copper. Elsewhere the predominating ore is chalcopyrite, 
and, to a less extent other sulphides, below the water line, but 
above this carbonates and silicates predominate. As to the 
mode of occurrence, copper is found in segregated veins in 
the metamorphic rocks, in fissure veins and contact deposits 
principally in other rocks, and also, in some cases, in the 
metamorphics. There is an almost universal association 
with igneous rocks, and, in some cases, this can be shown to 
be due to the presence of the igneous rocks, while, in other 
instances, this relation seems probable. While this associa- 
tion is at times a true contact effect, it is generally the result 
of a secondary process of concentration. Usually the copper 
is associated with other sulphides, chiefly blende and galena, 
and very commonly it is argentiferous and auriferous. This 
association with other metals is particularly common in the 
fissure veins, and sometimes one, sometimes another, of the 
sulphides predominates. 



222 ECONOMIC GEOLOGY OF THE UNITED STATES. 

While in most cases the ores of copper are associated with 
igneous rocks, this is not invariably the case, as, for instance, 
in the Mansfield mines of Germany. In such places the ore 
may have been precipitated from a copper solution when the 
strata were deposited, and subsequently concentrated ; or it 
may have been concentrated from some extraneous sedimen- 
tary source, as is so commonly the case in iron ore beds. 
Analyses show copper in igneous, sedimentary, and meta- 
morphic rocks, and in some cases its presence can be detected 
with the eye. Therefore, any of these rocks may serve as a 
source of copper, although its predominance in igneous rocks 
and their greater liability to decay and alteration, with the 
consequent formation of various soluble salts, make these 
the most common source. 

Uses of Copper. — Since prehistoric times copper alloyed 
with' tin has been used in various parts of the world for the 
manufacture of bronze. Thus it was used for this purpose 
in Homeric times, and it is found in the lake dwellings of 
Switzerland. The bronze found in Troy contains very little 
tin, and since this metal is not found in the excavations in the 
west, it seems probable that the bronze was made in Asia, 
perhaps in China or India, by some secret process and 
imported to the western countries. 

By an alloy of copper and tin, although both metals are 
soft, a comparatively hard metal is produced. The properties 
of this alloy, bronze, vary greatly according to the proportions 
of the two metallic constituents, and these vary with the use 
for which the alloy is intended. United States ordnance is 90 
per cent copper to 10 per cent of tin, and ordinary bell metal 
is about 80 per cent copper, though the percentage varies with 
the tone required. Statuary bronze is generally an alloy of 



copper. 223 

copper, tin, and zinc ; and, in these various bronzes, the colour 
varies from copper-red to tin-white, passing through an orange- 
yellow. A bronze containing two per cent of phosphorus 
makes a metal which is claimed to be equal to the best steel. 
There are many hundred different kinds of bronze, and every 
year many patents are granted for new bronzes. 

An alloy of copper and zinc produces brass, which is found 
of so much value for small articles used in building and for 
ornamental purposes in machinery. Copper is also used in 
roofing and plumbing, and at one time an extremely impor- 
tant use was for sheathing vessels below the water line. This 
is still in use, by some vessels, but the demand for copper for 
this purpose is distinctly decreased by the introduction of 
iron vessels and by the substitution of a copper paint. 

A large supply of this metal is made into copper wire ; 
but the most important present use of copper is in electricity, 
for which its high conductivity especially fits it for the con- 
duction of electric currents. With the introduction of elec- 
tricity into nearly every industry, and particularly by its wide- 
spread adaptation to lighting and transportation, the demand 
for copper has increased at a marvellous rate in the past ten 
years, a rate which has been attained by no other single use 
of any metal. Whether the demand will continue at the 
same rate, and if so, whether the supply will correspondingly 
increase, are questions of great interest which will probably 
be answered in the affirmative. The continued rapid exten- 
sion of electricity seems certain, and the supply of copper 
is apparently unlimited, yet it is a question whether it is 
expedient for our great mines to exhaust their supplies, for 
the benefit of a foreign market, at a low price, while there is a 
danger that in the future we may need the supplies ourselves. 



224 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



The price of copper (Lake Superior copper) has varied 
greatly since 1860, when it averaged 22^ cents per pound. 
During 1864 it averaged 46^ cents, and in July of that 
year was sold at 59| cents. There was, however, a gradual 
though fluctuating decline to 1886, when the price reached 
11 cents. In 1888 the price reached 17J cents, but fell 
again in 1889, then rose, and during 1892 the average price 
was 11 \ cents per pound. The fluctuations, in the period 
immediately succeeding 1887, were due to the manipulation 
of a French syndicate. Now, owing to an understanding 
between the leading copper-producers of the world, which 
limits the production and exportation, a moderately uniform 
price is assured. 

The United States consumed, in 1860, 14,232,000 pounds 
of copper; in 1870,24,684,000 pounds; in 1880, 53,598,000 
pounds; in 1890, 190,541,676 pounds; and in 1892, 266,895,715 
pounds, this recent immense increase being chiefly due to the 
demands of electricity. 

Production of Copper. — The following tables illustrate the 
distribution of the copper output of the world : — 

PRODUCTION OF COPPER IN THE UNITED STATES. 
Pounds. 



States. 


1882. 


1885. 


1888. 


1890. 


1892. 


Montana . . . 


9,058,000 


67,797,864 


98,504,000 


110,996,000 


164,300,000 


Michigan 






57,131,000 


72,759,000 


86,503,000 


100,695,000 


107,300,000 


Arizona . . 






17,9S4,000 


22,706,366 


33,200,000 


34,900,000 


38,000,000 


Colorado 






1,494,000 


1,146,000 


1,621,000 


6,000,000 


7,250,000 


California . 






827,000 


469,000 


1,570,000 


1,600,000 


3,200,000 


Utah . . . 






606,000 


126,000 


2,131,000 


600,000 


2,000,000 


New Mexico 






869,000 


80,000 


1,631,000 


870,000 


500,000 


Total for the j 
United States ' 


90,794,000 


166,4S6,230 


228,501,000 


259,861,000 


325,180,000 













copper. 225 

Of the Montana supply in 1892, 100,000,000 pounds came 
from a single mine, the Anaconda, and more than 30,000,000 
from the Boston and Montana. In 1891 Michigan produced 
over 1,000,000 pounds more copper than Montana, but since 
1887, with this exception, Montana has produced more than 
Michigan. Since the beginning of 1883 Arizona has held 
third place, although its output has steadily increased. In 
1890 Maine, New Hampshire, and Vermont produced to- 
gether 378,840 pounds of copper, and in 1892, outside of the 
states and territories in the above table, only 2,500,000 
pounds were produced in the country. 

COPPER PRODUCTION OE THE UNITED STATES. 
Long Tons (2240 Lbs.). 

Year. Amount. Value. 

1846 . -. 150 

1850 650 

1860 7,200 

1870 12,600 

1880 27,000 $11,491,200 

1885 74,324 18,292,999 

1890 116,009 30,930,800 

1892 145,170 37,850,000 

In 1846 the Lake Superior mines produced 26 per cent of 
the copper of the country ; in 1870, 87.2 per cent ; and since 
this time the percentage has rapidly decreased, until in 1891 
only 40.2 per cent of the output of the country came from 
this district, while in 1892 the percentage was much smaller. 
During the year 1892 the United States imported copper to 
the value of $730,384, while it exported $10,162,870 worth 
of this metal. The imports, which come mainly from Canada 
and Spain, are chiefly ores which are smelted in the United 
States. Our supply therefore greatly exceeds our needs. 



226 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



COPPER PRODUCTION IN THE WORLD. 
Long Tons (2240 Lbs.). 



Countries. 


1879. 


1883. 


1887. 


1890. 


1892. 


United States . . . 


23,350 


51,570 


79,109 


116,009 


145,170 


Spain and Portugal 




33,361 


44,607 


53,706 


51,700 


46,600 


Chili 




49,318 


41,099 


29,150 


26,120 


20,000 


Japan 










3,900 


7,600 


11,000 


15,000 


18,000 


Germany 










9,000 


14,643 


14,875 


17,800 


16,687 


Australia 










9,500 


12,000 


7,700 


7,500 


7,700 


Mexico . 










400 


489 


2,050 


4,325 


7,663 


Africa 










4,328 


5,000 


7,250 


6,450 


6,728 


Russia . 










3,300 


4,400 


5,000 


4,800 


5,000 


Venezuela 










1,597 


4,018 


2,900 


5,640 


3,021 


Total for World 




151,963 


199,406 


223,798 


269,615 


291,474 



The noteworthy features of this table are the remarkable 
increase of the production in the United States, the steady 
increase of the Japanese output, the increase in Mexico, 
since the opening of the Boleo mine in 1887, and the steady 
decline of the Chilian copper production. 



COPPER PRODUCTION BY CONTINENTS. 
Long Tons (2240 Lbs.). 



Continents. 


1884. 


1886. 


1889. 


1891. 


North America. . 


63,903 


73,845 


110,134 


137,864 


Europe .... 


75,224 


75,203 


84,843 


81,210 


South America . . 


48,269 


40,088 


31,983 


29,015 


Asia 


10,000 


10,000 


15,000 


17,000 


Africa .... 


5,260 


6,125 


7,860 


6,020 


Australasia . . . 


14,000 


9,700 


8,300 


7,500 


Total . . . 


218,756 


214,961 


258,120 


278,609 



copper. 227 

The African supply comes from Cape of Good Hope, the 
Asiatic from Japan, the European chiefly from Spain, 
Portugal, and Germany, the South American mainly from 
Chili and Venezuela, and the North American almost entirely 
from the United States. 

COPPER PRODUCTION OF THE WORLD. 
Long Tons (2240 Lbs.). 

1879 151,963 

1881 163,369 

1885 225,592 

1888 258,026 

1890 269,615 

1892 291,474 

It is a remarkable increase in the production of an im- 
portant metal, which nearly doubles the output in fourteen 
years, and this could be made possible only by a marked 
increase in the uses of the metal. It is a striking fact 
in this connection that the price has fallen in this period 
less than 6 cents, or from an average of 17-J- cents for the 
year 1879 to 11| cents in 1892. Of the total output of 
291,474 tons in 1892, the United States supplies nearly 
one-half. 



CHAPTER X. 

LEAD AND ZINC. 

Lead. 

General Statement. — The ores of lead and zinc are almost 
inseparably associated; for, with very few exceptions, the 
mines of the one contain the other, although usually one of 
the two predominates. The metals are, however, considered 
separately in this case. There are two general sources of 
lead, the argentiferous and the non-argentiferous galena, the 
latter being found usually in association with zinc blende, 
and both of these lead ores being weathered near the sur- 
face to the carbonate cerrusite, the sulphate anglesite, etc. 
Where the ore is argentiferous, it is generally found in fis- 
sure veins or near some eruptive rock, but the non-argen- 
tiferous galena occurs commonly in stratified rocks. 

As in the case of gold, silver, and copper, the principal 
source of this metal is the Cordilleras, but the states of the 
Mississippi valley are also important producers. In the 
former region the ore is chiefly silver and gold bearing, in the 
latter it is non-argentiferous and is associated with zinc. 
Were it not for the presence of the precious metals in much 
of the Cordilleran galena, it is doubtful if the output from 
these states would be so great. Non-argentiferous galena 
can be profitably obtained only where it is easily mined or 
where it exists in considerable quantities. 

228 



LEAD AND ZINC. 229 

Appalachian District. — From Maine to Georgia galena 
occurs in the metamorphic rocks; and at numerous points 
in this belt mines have been opened in these veins. Some 
of these have been exploited for many years, and even made 
to produce fair returns, but very few are open at present. 
The ore occurs generally in small veins, sometimes segre- 
gated, but it is usually not sufficiently argentiferous nor 
extensive enough to make mining profitable. Moreover, the 
veins are not always permanent, and they usually become 
poorer as the depth increases. This region never will become 
important in the production of lead, but it may, in time, 
become of more importance than it is at present. 

Missouri Lead District. — In various parts of Missouri, 
Kansas, Wisconsin, Illinois, and other neighbouring states, 




mm 



Fig. 20. — Ideal section showing mode of occurrence of lead in Wisconsin. 
a, a, lead-bearing stratum. 

lead and zinc are found, free from association with the pre- 
cious metals, in the ores galena and blende. The region is 
one of slightly disturbed sedimentary rocks, of an age vary- 
ing from Cambrian to Carboniferous. Certain strata of lime- 
stone, of a dolomitic character, are ore-bearing, those in the 
upper part of the region being the Galena limestone of 
Lower Silurian age, and in the lower part strata of the 
Keokuk group of the Lower Carboniferous. When the Mis- 
sissippi valley was first explored, lead was found in boulders 
on the surface, and this added zest to the early explorations 
for the precious metals, which, however, were never found 



230 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



in this region. The early settlers in the valley found this 
lead of great value in the manufacture of shot and bullets, 
since the transportation of this heavy metal, from the sea- 
shore through the wilderness, was a very difficult task. At 
first the lead was smelted by very primitive methods and 
moulded into the required form, but before the beginning of 
the present century, a shot tower was erected there. Actual 



%^^hr^^~y 







Fig. 21. — Ideal section showing forms of "openings" and ore deposits in the 
Galena limestone, Wisconsin, a, vertical crevice opening; b, cave opening; 
c, gash vein ; d, d, d, flat openings. (After Chamberlain.) 



mining was first begun near St. Louis, but it was not long 
before mining operations were extended into the neighbouring 
states. 

The ore occurs in the nearly horizontal limestones in flat 
openings parallel with the bedding, in gash veins of variable 
size at right angles to this, and in caves in the limestone. 
Fossils are not uncommonly found replaced by galena or 



LEAD AND ZINC. 



231 



blende, and in the caves actual stalactites of galena occur. 
These facts show that the ore has been gathered together 
since the formation of the limestone ; and as it is confined 
to single strata over wide areas, it is certain that its origin 
is either from the ore-bearing stratum or from the strata 
immediately above or below, probably the former. 1 

As we proceed in the study of lead-zinc deposits, it will 
be found that this is a common mode of occurrence in various 




Fig. 22. — Section showing flats (a) and pitches (c) in Galena 
limestone, Wisconsin. (Modified from Chamberlain.) 

parts of the world, and it must be granted that, in certain 
limestones, usually dolomitic limestones, there was a store of 
disseminated zinc and lead, which, under favourable circum- 
stances, was accumulated into these deposits. Sea-water 
contains these metals, and they may have been precipitated 
from solution, or certain animals may have extracted them 

1 Recent studies show that there are small fissures connected with these 
deposits and that. they have in part influenced the ore accumulations; but 
this does not essentially modify the above conclusions. 



232 



ECONOMIC GEOLOGY OF THE UNITED STATES. 




from the water and built them into their calcareous skeletons. 
A plausible and rather attractive theory is that the source 
is from sea-weeds, which at present are known to contain 
these metals. This theory assumes that in the sea, over the 
point where the ore-bearing limestone was being deposited, 

a Sargassum sea existed, as is the 
case in the central North Atlantic 
and other oceans, in the swirl en- 
closed by oceanic currents. The 
Mississippi valley, in the Palaeozoic, 
was occupied by a great ocean 
bounded by land areas on the 
north, east, and west, and such a 
condition may well have existed 
there. If such an accumulation of 
sea-weed did exist in this region, 
the constant decay of the vegeta- 
tion might have furnished to the 
ocean bottom a supply of both these metals, but it must be 
admitted that this is merely hypothesis. The facts are that 
in some way zinc and lead were incorporated into these strata, 
and later segregated, but by just what means we cannot say. 
Even from the very first, these deposits have been worked 
by individuals or small companies as superficial open-work 
mines. The conditions do not favour the formation of large 
companies, because the mining operations are simple, very 
little machinery is called for, drainage is easily obtained, and 
no deep or extensive tunnels and shafts are needed. More- 
over, the ore is found in irregular accumulations, sometimes 
yielding large returns, but often being absent. These con- 
ditions have led to the general adoption of this system, each 



Fig. 23. — Section showing gash 
vein (a), cave opening (&), 
and flat opening (c), in the 
Galena limestone. (Modi- 
fied from Chamberlain.) 



LEAD AND ZINC. 233 

land-owner working his own area or leasing it to others on 
shares. Recently, however, the mining operations have been 
extended by the discovery of the ore, in borings, at consider- 
able depths, and even beyond the limits of the original lead- 
producing belt. By these means the district is becoming 
more productive. 

Colorado Lead Mines. — The Leadville silver-lead vein, in 
the Mosquito Range, at the head-waters of the Arkansas 
River, has been one of the remarkable lodes of the country ; 
and this gave to Colorado its first important start as a 
mining state. From an area of about a square mile the 
output of silver has been, for a number of years, greater than 
that of any foreign country, with the exception of Mexico. 
During the same period the production of lead has been 
nearly equal to that of England, and greater than any other 
European country excepting Spain and Germany. In 1860 a 
placer deposit of stream-gold was found, in a gulch near this 
lode, and several million dollars' worth of this metal was ex- 
tracted, causing the establishment of a nourishing town 
called Oro, which, however, soon lost its importance when 
the gold began to be exhausted. Not until 1875 was the 
carbonate of lead, which has since been so important, ac- 
tually recognized. 

There are several modes of occurrence in this vein; but 
the typical one (Fig. 24) is between a bed of blue-gray dolo- 
mitic limestone of Lower Carboniferous age, for a foot wall, 
and a sheet of porphyry for the hanging wall, the dip being 
extremely variable, from steep to very gentle. The upper 
wall is sharp and distinct, but the ore passes by gradual 
transition into the underlying limestone. Argentiferous ga- 
lena, bearing native gold, is the actual ore, but above the 



234 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



water line this is weathered to the carbonate and sulphate. 
The gangue is limestone, barite, and chert, with ores of anti- 
mony, molybdenum, copper, bismuth, zinc, etc. Through this 
the ore is distributed irregularly, the lead ore being chiefly in 
the limestone, the copper and gold in and near the eruptives 
and crystallines. Mr. Emmons, 1 who has studied this vein, 
has arrived at the conclusion that the ore was deposited in 
the form of sulphides in the overlying quartz porphyry, 




Fig. 24. — Cross-section of Evening Star Mine, Carbonate Hill, Leadville, Colo- 
rado, a, recent deposits; b, porphyry; c, white porphyry; d, white lime- 
stone; e, vein material in blue limestone stratum; /, fault; o, ore; t, quartz- 
ite ; v, blue limestone ; x, lower quartzite. (After Emmons.) 



and afterwards leached from this by percolating water. The 
strata are faulted ; but since ore is not found in the faults, 
the necessary conclusion is that they were formed after the 
accumulation of the ore. An easy passage-way for the 
metalliferous solutions was furnished along the contact plane 
of the porphyry and limestone ; and this served as an ore 
channel, in which the minerals were deposited, and from 
which they penetrated both the porphyry and the limestone, 



1 Monograph, U. S. Geol. Survey, Vol. XII. 
Industry of Leadville, Colorado. 



1886, Geology and Mining 



LEAD AND ZINC. 235 

but particularly the latter, replacing it atom by atom. Ac- 
cording to this explanation, the vein is, therefore, partly an 
ore channel, partly a replacement deposit, and not a contact 
vein, as might at first appear probable, although there seems 
every reason to believe that the intrusion of some of the 
igneous rocks in the neighbourhood furnished heat to the 
percolating waters. 

The Leadville mines have exhausted the best of their 
easily mined carbonate ; and in the future the output from 
this district will probably continue to decrease, as it has in 
the past few years. However, other mines are in operation, 
and new ones continually being opened. What permanent 
effect the recent fall in price of silver will have upon 
these mines cannot at the present time be stated ; but it 
will not be surprising if it serves to close many of the 
lead-silver mines, and to reduce the output of lead from 
these sources. 

Other Western Lead Mines. — The lead veins of the west 
are practically all argentiferous galena ; and the description 
of the Leadville mine, together with that of the Eureka 
and other mines in the chapter on silver will serve to illus- 
trate these modes of occurrence. Utah is next in impor- 
tance to Colorado, and some of the mines of this territory, as 
well as of Idaho, have already been mentioned. Idaho is 
producing large quantities of this metal, principally from the 
famous Cceur d'Alene mine, which, in 1891, had an output 
of about 66,000,000 pounds of lead from a low-grade silver- 
lead sulphide, which exists in great quantities, and promises 
in the future to increase in importance. The ore occurs in 
metamorphic quartzites and schists which have been folded 
and faulted, and the gangue is siderite. Montana, Arizona, 



236 ECONOMIC GEOLOGY OF THE UNITED STATES. 

and New Mexico also produce lead from their argentiferous 
galena mines ; and, in smaller quantities, this metal is obtained 
from the other states of the Cordilleras. 

Foreign Lead Mines. — Spain is the leading lead-produc- 
ing country of the world, and here, as in the United States, 
there are two sources, — the argentiferous and the non-argen- 
tiferous ores. The most important non-argentiferous galena 
district is in the province of Jean, which produces nearly 
two-fifths of this class of Spanish ore. Here the lead occurs 
in true fissure veins, which traverse a series of nearly hori- 
zontal Triassic sandstones, and an underlying granitic mass. 
A very little silver and some blende occur, the gangue 
being quartz. Of even more importance than this district 
is the province of Murcia, where the ore is found in nearly 
vertical fissure veins traversing Silurian slates, limestones, 
and intrusive trachytes. The ores are partly argentiferous, 
partly non-argentiferous galena, in a gangue of quartz, calcite, 
and barite. A third important mine is in the province 
of Almeria, where galena, chiefly non-argentiferous, occurs 
in metamorphic rocks. Portugal has deposits not unlike 
those of Spain, but of much less importance. 

Germany produces lead, usually argentiferous, from the 
famous veins which have already been mentioned under 
silver, in the Harz, Erzgebirge, etc. (Clausthal, Rammels- 
berg, St. Andraesberg, Freiberg, etc.), and also from the 
Rhenish provinces, particularly Westphalia. Here galena 
occurs in nodules and grains cementing a Devonian sand- 
stone ; and near Cologne in Silesia lead sulphide, accom- 
panying blende, is found in limestone. The most important 
source of this metal is in the fissure and segregation veins 
of the great mining districts, already referred to, where 



LEAD AND ZINC. 237 

copper, zinc, silver, lead, and other metals all occur together. 
In Europe, the next most important lead-producing country 
(Mexico and New South Wales are more important) is 
Great Britain. Both the Cornwall and Devonshire districts 
are lead-producers, but they are losing importance in this 
respect. Twenty-five years ago Devonshire had an annual 
output of over 1000 tons of lead, and Cornwall over 
6000 tons, but now the output is much less. Elsewhere 
in England galena is found in flats and fissures in limestone. 
In north England two sets of fissure veins cross the Carbo- 
niferous limestone, and from these there are branching flats, 
which sometimes lead to caverns, these being connected 
with the fissures by thin stringers or leaders. The gangue 
is calcite and quartz, and it also contains some blende. 
Nearly the same occurrence is noticed in Yorkshire, and lead 
is also found in Wales, Scotland, and Ireland, in nearly the 
same modes of occurrence as in England. 

In Italy and Belgium galena is found associated with 
zinc blende in modes of occurrence which are described 
in the latter part of this chapter. On the mainland of 
Italy galena also occurs in gneiss with very little blende, 
and in Belgium a lead vein crosses both the Carboniferous 
limestone and the Coal Measures and sends branches between 
the contact of the two. Austria-Hungary produces both 
zinc and lead, from the large veins, already mentioned in 
a previous chapter, and from a deposit of dolomite. Neither 
Russia, Sweden, nor France are of marked importance in 
the production of this metal, but each produces some. The 
supply from Russia is obtained partly from argentiferous 
galena veins and partly from the Polish zinc-lead deposits. 
Sweden produces argentiferous galena from the metamor- 



238 ECONOMIC GEOLOGY OF THE UNITED STATES. 

phic rocks, and France also has argentiferous lead veins 
crossing metamorphics and eruptives. 

Important deposits of lead occur in New South Wales, 
but we know little about the mode of occurrence there, 
excepting that the supply comes chiefly from silver-lead 
mines. Mexican lead ores are partly smelted in this country, 
and our knowledge of the position of the industry, as well 
as the occurrence of the ore, is obscure. 

Origin of Lead Ores. — Like all metals, the original source 
of this one was probably igneous rocks, although it has come 
into its present position in a variety of ways. The metal 
easily oxidizes, and forms soluble salts, which readily find 
their way into sedimentary rocks. It may be said that lead 
deposits are found in three principal modes of occurrence: 
first, in fissures or other cavities through which metalliferous 
solutions pass ; secondly, in segregated veins where rocks 
are metamorphosed ; and thirdly, in local deposits derived 
locally from mineral originally disseminated. The first two 
are generally argentiferous, while the third is usually associ- 
ated with zinc. These occurrences are more fully described 
in the chapters on silver and zinc. 

Uses of Lead. — This metal finds numerous uses in the arts, 
and these are being extended and increased every year as 
the output increases. White lead, the carbonate, to be used 
in paint, still continues to be the most important use of lead, 
and litharge, the oxide of lead, is also made into paint; but 
much of the supply of this metal is manufactured into pipe 
and sheet lead for plumbing and various other purposes. 
These latter uses of the metal are favoured by its low 
melting-point, its softness, the ease with which it can be 
soldered, and the fact that it does not rust extensively. 



LEAD AND ZINC. 239 

An alloy of lead and arsenic 1 makes lead harder, more 
fusible, and gives to it the habit of assuming a spherical 
form when dropped through the air. This alloy is used in 
the manufacture of shot, and this industry calls for large 
annual supplies of lead. Other alloys are used for various 
purposes, but the only very important combination is the 
type metal alloy, which is a mixture of lead and antimony, 
at the ratio of 76 to 24. 2 This reduces the melting-point 
below the average of the two, makes the alloy harder than 
lead, and gives to it the power of expanding on cooling so 
that it can be cast, a power which lead alone does not 
possess. The manufacture of type metal is a delicate proc- 
ess, since, if too much antimony is used, the alloy is too 
hard, and it becomes too soft if the proportion of antimony 
is too low. Under the heat of melting to form the alloy, 
the antimony may be partly oxidized and lost, and this has 
to be avoided by careful methods. 

The price of lead has steadily decreased, with some fluc- 
tuations, since 1870, when it was 6.25 cents a pound, to 
1892, when it averaged 4.09 cents for the year, but in 
December was 3.80 cents. During this time it has never 
been above 6.55 nor below 3, but has averaged about 5 cents. 

Production of Lead. — The available statistics for this metal 
are not so complete as for those previously considered, 
nor is the metal of as much importance. Since the lead is 
so frequently smelted from other ores, and since much of 
it is made into white lead, it is difficult to estimate the value 
of the industry. The following tables will, however, serve 
to illustrate the distribution of lead and the changes in 

1 Three parts of arsenic to 700 parts of lead. 

2 There are numerous varieties of type metal of varying composition. 



240 



ECONOMIC GEOLOGY OE THE UNITED STATES. 



output of the different districts, and this is the chief object 
of the tables of statistics in this treatise. 

PRODUCTION OF LEAD IN THE UNITED STATES. 

Short Tons (2000 Lbs.)- 



States. 


1873. 


1875. 


1880. 


1885. 


1890. 


1891. 


1892. 


Colorado 


56 


818 


35,674 


55,000 


54,500 


64,000 


61,500 


Utah 


15,000 


19,000 


15,000 


23,000 
15,000 


18,000 
33,000 


28,000 
40,000 


30,000 
36,500 


Idaho-Montana 






Mississippi * valley .... 


22,381 


24,730 


27,690 


21,975 


31,351 


34,000 


37,000 


Nevada 






16,690 


3,500 


2,000 


2,500 


2,500 


Arizona-California 








4,000 


1,500 


2,000 


2,000 


Total 


42,540 


59,540 


97,825 


129,412 


143,876 


178,133 


178,S92 



The remarkable increase in the output of Colorado is note- 
worthy, although since 1889 there has been a considerable 
decrease. Utah has steadily increased, as has also the Idaho- 
Montana production. This comes principally from Idaho, 
and the decrease in 1892 was due to the disastrous strike 
in the Cceur d'Alene mine, which caused the suspension of 
mining operations for several months. Nevada shows a 
marked falling off in lead production, as indeed it does in 
nearly all industries. During the year 1892, in addition to 
the output above enumerated, 9392 tons of lead were pro- 
duced by other states and territories, chiefly from New Mex- 
ico, and about 39,608 tons were produced from Mexican ores 
smelted in this country. 

1 The estimate for the Mississippi valley includes all of the non-argen- 
tiferous ores ; but most of them are from the states in the lead-bearing dis- 
trict of the Mississippi valley, although a small amount comes from the 
Appalachian states. 



LEAD AND ZINC. 



241 



The following table from the census statistics, based upon 
a study of the mines and an estimate of the lead contents, 
shows the distribution of the lead production by states : — 

LEAD PRODUCTION IN THE UNITED STATES, 1889. 



States. 


Short Tons 
(2000 Lbs.). 


Value at Place 
of Production. 


Colorado 

Missouri 

Idaho 

Utah 

Montana 

New Mexico 

Kansas 

Arizona 

Nevada 

Wisconsin 


70,788 

44,482 i 

23,172 

16,675 

10,183 

4,764 

3,617i 

3,158 

1,994 

l,678i 


2,101,014 

1,571,161 

1,042,629 

763,329 

456,975 
170,754 
103,236 

98,747 
72,653 
64,062 



PRODUCTION OF LEAD BY THE UNITED STATES. 



Years. 


Short Tons 


Mexican Ore 


Total Value at 


(2000 Lbs.). 


SMELTED IN U.S. 


New York. 


1825 


1,500 






1835 


13,000 










1845 


30,000 










1855 


15,800 










1865 


14,700 










1870 


17,830 










1876 


64,070 










1881 


117,085 






$11,240,160 


1886 


135,629 






12,667,749 


1889 


157,397 


25,570 


16,137,689 


1890 


143,876 


18,124 


14,266,703 


1891 


178,133 


23,867 


17,574,000 


1892 


178,892 


39,608 


17,917,000 



1 Lead ore. 



242 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



With some fluctuations the United States has thus steadily 
increased its output since 1825 ; but between 1870 and 1880, 
when the mines of the Cordilleras became of importance, 
there was a very striking increase. In 1892, 142,087 tons 
of the total lead product came from desilverized ores. 

PRODUCTION OF LEAD IN THE WORLD. 

Metric Tons (2204 Lbs.) are used for All but the United States 
and Mexico, where Short Tons are used. 



Countries. 



1885. 



1887. 



1889. 



1890. 



1891. 



Spain 

United States . . 
Germany . . . 
Mexico 1 • . . . 
New South Wales 2 
Great Britain . . 

Italy 

Austria- Hungary . 
Russia .... 
Sweden .... 
Canada .... 



78,986 

129,412 

93,134 

194 
38,399 
16,461 
10,625 

714 



119,932 

145,212 

94,921 

15,488 

38,411 

17,795 

9,605 

988 

282 

93 



162,000 

157,397 

100,601 

25,570 

35,146 

36,189 

18,165 

10,603 

578 

254 

75 



163,838 

143,876 

101,781 

18,124 

41,996 

34,139 

17,768 

9,552 

838 

310 

51 



235,000 

178,133 

95,615 

23,867 

56,304 

32,731 

18,500 

8,683 

900 

299 

267 



1 Mexican statistics are not obtainable, because part of the ores are 
smelted in this country. Recently smelters have been established in 
Mexico which The Mineral Industry estimates will produce in 1893 about 
45,000 tons of lead, having smelted something like 35,000 tons in 1892. 
The statistics for Mexico are based upon the lead product from ores smelted 
in the United States, and are therefore far below the truth. 

2 No statistics are at hand for the output of lead in New South Wales, the 
estimate given above being the exported lead, and it is consequently less than 
the actual production. 

The United States includes only lead of domestic production, excepting 
in 1885, when Mexican ores are included. 



LEAD AND ZINC. 243 

A remarkable increase is noticed in the Spanish pro- 
duction, which has exceeded that of the United States, 
and given to Spain the first place, which the United States 
held for awhile. The rapid increase in the production of 
New South Wales and the steady decline of the British 
production are also striking. Mexico should probably hold 
fourth place in the table, although exact statistics cannot 
be given. The total production of lead in the world in 
1891 was probably about 650,300 tons. 

Zinc. 

General Statement. — Zinc is found chiefly in the ore 
sphalerite, or blende, the sulphide of zinc ; but in nearly all 
mines of this metal other ores, chiefly weathered forms, are 
found, the most important of these being willemite, the 
silicate ; calamine, the hydrous silicate ; and smithsonite, the 
carbonate. In the New Jersey mines the ore is the red oxide 
zincite, and willemite, with the zinc-iron oxide franklinite. 
Blende occurs usually in association with galena, the latter 
generally predominating in the fissure veins, the former in 
local deposits derived from the enclosing strata. The former 
mode of occurrence has been described in the chapter on 
lead, and some of the descriptions which follow, being prin- 
cipally of lead-zinc deposits, must be considered to apply, in 
general, to lead. When blende is associated in minor quan- 
tities with lead, it can be extracted where economic methods 
are in use, but in our western silver-lead mines, blende is not 
found in sufficient quantities to be of much value. There- 
fore the Cordilleras have produced practically no zinc, 
although this metal may exist there as veins of blende, 



244 ECONOMIC GEOLOGY OF THE UNITED STATES. 

which have escaped the notice of the prospectors, who would 
not be familiar with its appearance, the ore being non- 
metallic in lustre. In distribution, zinc differs widely from 
the last four metals, the chief source being the states of the 
Mississippi valley and one or two eastern states, notably 
New Jersey and Pennsylvania. 

Zinc in the United States. — No further description of the 
lead-zinc deposits of the Mississippi valley is called for, 
since the blende and galena are found together in the same 
stratum, often in intimate association. Nevertheless, especial 
attention is called to the description in the preceding section 
of this chapter, for comparison with the mode of occurrence 
in some of the foreign zinc mines. From this general region 
the chief supply of zinc comes from the Joplin district, in 
southwestern Missouri, and across the line in Kansas, where 
much progress has recently been made in the exploration of 
the deposits in the Keokuk group. 

Next to the mines of the Mississippi region the New 
Jersey zinc deposits are the most important in this country. 
This district includes two general mining areas situated 
close together, in Sussex County, one at Franklin Furnace, 
the other a few miles south of this at Ogdensburg. In both 
mines the ore is zincite, willemite, and franklinite, and the 
gangue calcite, included in nearly vertical beds of white 
limestone closely associated with, and for a long time sup- 
posed to be enclosed in, Archean gneisses. Not far distant 
from the mines there are igneous masses, and recent studies 
seem to show that the white crystalline limestones are not 
Archean, but Cambrian beds, metamorphosed by the intrusion 
of these igneous rocks, which are mainly granites. In the 
neighbourhood there are large areas of a blue dolomitic lime- 



LEAD AND ZINC. 245 

stone of Cambrian age, which is not metamorphosed, and it 
is this which is believed, by those who have most recently 
studied the region, to have furnished the zinc during a com- 
plete alteration to white crystalline limestone. In the blue 
limestone, blende is sometimes found cementing a breccia. 
The vein itself appears to be of true segregation origin, and 
the walls are not distinct, but the vein becomes poorer on 
either side, until only here and there a crystal or nodule of 
ore is found. Studies of these mines have convinced the 
author that segregation, as illustrated here, is a process, 
partly of replacement, partly of crowding the enclosing 
minerals aside to give room for those which are forming. 

Another important zinc mine is found in the Saucon 
valley, Pennsylvania, and this is also in the blue magnesian 
limestone, which has been very much fissured and crushed, 
the ore being deposited between the brecciated fragments. 
The ore in the upper parts of the mine is calamine, but it 
changes below to blende. From 1853 to 1876 this mine 
produced considerable zinc, but since then it has been of 
very little importance. In southwestern Virginia calamine 
occurs in crystalline limestone, and probably the ore here 
also changes to blende. Other zinc mines in the United 
States are of little importance. 

Foreign Zinc Mines. — Considerable zinc is found in Bel- 
gium and the Rhenish provinces of the German Empire. 
The ore in Belgium is chiefly calamine, although other ores 
also occur. It is found at Bleiberg, in small veins and irregu- 
lar masses, in a Carboniferous limestone crossed by a fissure 
vein which has been filled with brecciated fragments, partly 
cemented by ore, and then later reopened and again filled. 
Both blende and galena occur there. Near Aix la Chapelle 



246 ECONOMIC GEOLOGY OF THE UNITED STATES. 

a bed of zinc occurs in Carboniferous dolomitic limestone, 
which it has partly replaced. The ore is calamine occurring 
in lake-like depressions in the strata. This region, which 
was exploited in the fifteenth century, has produced more 
than 1,500,000 tons of remarkably pure zinc ore. Near 
Cologne this metal is found, in the form of blende, with 
galena, in basin-like depressions. 

A very important zinc-producing region is in Silesia, in 
Germany, and extending into the neighbouring country of 
Poland. Here both calamine and galena occur in troughs, in a 
dolomite (Muschelkalk), evidently the result of concentration 
from the dolomite. The calamine changes below to blende, 
and kernels of this mineral are found enclosed in calamine, 
showing plainly that the latter is derived from the former by 
weathering. This same bed of Muschelkalk produces zinc 
elsewhere in Germany, and blende is found also in the Black 
Forest, replacing fossils, and also in the various lead mines 
of the nation. The chief supply of this metal in Germany 
comes, however, from Silesia and the Rhenish provinces. 

The statements concerning the lead occurrence of Great 
Britain apply also to zinc, since this metal is practically 
coextensive with the lead. Austria-Hungary has zinc in 
very nearly the same modes of occurrence as Germany, 
dolomite being at times the country rock, while, in other 
places, lead-zinc ores are found in veins traversing meta- 
morphic, igneous, and sedimentary rocks. Important zinc 
deposits occur in Italy, chiefly on the island of Sardinia. 
Here also the ore is calamine and blende associated with 
galena, occurring in a dolomitic limestone. Other Euro- 
pean countries, notably Sweden, produce some zinc, but 
none of them are of particular importance. Several zinc- 



LEAD AND ZINC. 247 

producing districts occur in Spain, the ores there also being 
calamine and blende. 

Outside of Europe and the United States very little zinc 
is produced ; but it seems hardly probable that this metal is 
confined to these two districts, and the fact that these are 
the two most explored and most accessible regions renders 
this still more improbable. There are no signs of exhaustion 
of our zinc ores ; but if they are exhausted, there need be 
little fear that their place will not be taken by new dis- 
coveries either in our western country, or in some other 
partly explored region. 

Origin of Zinc Deposits. — This metal, like many others, 
may be said to have a typical mode of occurrence, although 
it is true that there are variations from this. Ores of zinc, 
usually as minerals of secondary importance, occur in many of 
the deposits of other metals, particularly argentiferous galena. 
In such places the origin of the zinc is the same as that of 
the galena and other ores, whatever this may be. But when 
zinc predominates, or forms a considerable percentage of 
the ore, in the vast majority of important mines the associa- 
tion is with dolomitic limestone. It is not possible to state 
the exact meaning of this association. Dolomitic limestone 
is sometimes originally deposited as such, but at times it is 
the result of a secondary alteration of ordinary limestone. 
Admit that a limestone thus changing is zinc-bearing, and it 
is readily conceivable that, as one result of the alteration, 
the disseminated zinc may be segregated. Magnesian lime- 
stones, when originally deposited as such, are very fre- 
quently precipitated from solution in saline waters, usually 
dead seas. Such is the case with the Permian dolomites of 
Texas ; but in other dolomites the evidence points to accu- 



248 ECONOMIC GEOLOGY OF THE UNITED STATES. 

mulation in open seas where precipitation has probably not 
occurred. In these cases the magnesia may have been intro- 
duced by organisms which contained it in their tests or 
calcareous skeletons. 

Various hypotheses have been suggested to account for 
the mode of origin of the galena-blende deposits of the 
Mississippi valley, and these may with equal force be ex- 
tended to account for the zinc deposits elsewhere. There is 
a remarkably uniform association with dolomite, and from 
whatever source we may assume the original supply to have 
been derived, and these sources are probably various, subse- 
quent concentration, akin to the concretion of flint in chalk, 
has been brought about by the gathering together of the 
zinc from the dolomite, sometimes by metamorphism, as in 
New Jersey, sometimes by slow changes not strictly meta- 
morphic. Certain of the zinc deposits which occupy basins 
in the rock seem to have been precipitated in these positions 
originally, although it is possible that this is merely an 
appearance simulated by a deposit of secondary origin. 
These remarks apply with equal force to the associated 
galena. The striking feature of zinc, and of many lead 
deposits also, is the general association with sedimentary 
rocks and their accumulation without the intervention of 
the more potent vein-forming agencies. In this respect they 
differ from gold, silver, and copper, and more closely resem- 
ble iron. 

Uses of Zinc. — This metal, in the state of the oxide form- 
ing zinc-white, is used as a base for paint in the place of 
white lead. Formerly zinc was used for sheathing vessels, 
but very little is at present supplied for this purpose. For 
plumbing and roofing, zinc is in common use, and as a 



LEAD AND ZINC. 249 

coating to iron this metal is extensively called for in 
galvanizing. 

One of the most important uses is in the manufacture of 
brass, which is ordinarily composed of from 66 to 73 parts of 
copper and 27 to 34 parts of zinc. The composition varies 
entirely according to the use for which it is intended, and, 
with the variation in proportion, the colour becomes more 
golden or whiter, according as the proportion of copper is 
increased or decreased. With an increase in the proportion 
of zinc, the alloy becomes more fusible, harder, and more 
brittle. Brass was made long before zinc as a metal was dis- 
covered, and Aristotle says that the people by the Euxine 
Sea made their copper a beautiful whitish colour by mixing 
with it a white earth found there. Strabo also tells us that 
the Phrygians made brass in this way. 

Another alloy of zinc and copper in common use is white 
metal, in which zinc predominates. From this, buttons are 
frequently made. Imitation gold is also made by alloying 
zinc with a predominance of copper, varying from 77 to 85 
per cent of the mass, and this is in common use as "gold- 
foil " for gilding. Zinc is also made use of in the construc- 
tion of electric batteries. 

This metal is much less important than those hitherto 
considered, with the exception of platinum, and less is 
produced in the world. Since 1875 the price of spelter 1 
has gradually decreased from an average of 7 cents a pound 
to an average of 4.63 cents in 1892, and in December of 
that year the price was 4.40 cents a pound. 

Production of Zinc. — The available statistics for the pro- 
duction of zinc are not very satisfactory, for the reason 
1 Spelter is the commercial name for zinc. 



250 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



that it is frequently not smelted in the same state, or, at 
times, even in the same country, where it is produced. 
We have statistics for the production of spelter, but this 
shows little with reference to the distribution of the metal, 
which it is the purpose of these tables to illustrate. These 
statistics are introduced, however, as the best that can be 
obtained. The first table illustrates the spelter production 
in this country since 1882, but it will be noticed by com- 
parison with the second that this does not illustrate the 
actual distribution of the ore. 



PRODUCTION OF SPELTER IN THE UNITED STATES. 
Shokt Tons (2000 Lbs.). 



States. 


1882. 


1884. 


1886. 


1888. 


1890. 


1892. 


Illinois 

Kansas 

Missouri .... 

Eastern and Southern \ 
States . . . . / 


18,201 
7,366 
2,500 

5,698 


17,594 
7,859 
5,230 

7,861 


21,077 

8,932 

5,870 

6,762 


22,445 
10,432 
13,465 

9,561 


26,279 
16,380 
13,530 

11,153 


30,300 
23,088 
16,161 

13,751 


Total .... 


33,765 


38,544 


42,641 


55,903 


67,342 


83,300 



New Jersey and Pennsylvania furnish the greater part 
of the supply credited to the eastern and southern states. 
In 1873 only 7343 tons of spelter were produced in this 
country. 



LEAD AND ZINC. 



251 



PKODUCTION OF ZINC ORE IN THE UNITED STATES, 1889. 
Short Tons (2000 Lbs.). 



States. 


Short Tons. 


Value at Mines. 


Missouri 


93,131 

24,832 

39,575 

63,339 

12,906 

450 

130 

140 


$2,024,057 

400,568 

299,192 

175,052 

141,560 

3,600 

3,250 

2,520 


Wisconsin 

Kansas 

New Jersey and Pennsylvania . . 

Southern States 

Iowa 

Arkansas 

New Mexico 


Total 


234,503 


$3,049,799 



In 1892 the production from the Missouri-Kansas mines 
was 155,000 tons, valued at 13,519,225, showing a marked 
increase in this industry. 

PRODUCTION OF METALLIC ZINC AND ZINC-WHITE IN THE 
UNITED STATES. 





Zinc-White. 


Metallic Zinc 


Total 


Year. 


Metric Tons 
(2204 lbs.). 


Value. 


Metric Tons 
(2204 lbs.). 


Value. 


Value. 


1880 


9,171 


$763,738 


21,088 


$2,277,432 


$3,041,170 


1884 


11,797 


910,000 


34,976 


3,422,707 


4,332,707 


1888 


18,149 


1,600,000 


50,729 


5,500,855 


7,100,855 


1890 




1,600,000 


57,789 


7,474,962 


9,074,962 


1891 




1,600,000 


72,834 


8,058,405 


9,658,405 


1892 




1,200,000 


75,589 


7,703,580 


8,903,580 



252 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



PRODUCTION OF SPELTER IN THE WORLD. 
Long Tons (2240 Lbs.). 



Districts. 


1883. 


1885. 


1887. 


1889. 


1891. 


Rhine District and \ 
Belgium .... J 

Silesia 

United States . . . 
Great Britain . . . 

Spain 

Austria 

Poland 


123,891 

70,405 
32,837 
29,161 
14,671 
6,267 
3,733 


129,754 

79,623 
36,328 
24,299 
14,847 
5,610 
5,019 


130,995 

81,375 
44,946 
19,839 
16,028 
5,338 
3,580 


134,648 

85,653 
52,553 
30,806 
16,785 
6,330 
3,026 


139,695 

87,080 
71,662 
29,410 
18,360 
6,440 
3,760 



The total production of spelter in the world in 1891 
was over 350,000 long tons. That the tables of spelter 
production possess very little value as illustrations of the 
distribution of the output, is shown by the fact that Italy 
has no place in the above table, although it is third in 
rank of importance as a zinc-producing country, and the 
ore of zinc is, with the exception of sulphur, the most im- 
portant mineral production. The ore is entirely exported for 
reduction, and serves to swell the amount of spelter accred- 
ited to other countries, just as in the first table Illinois 
is the largest spelter-producer, although zinc is not mined 
in the state. 






CHAPTER XL 

MERCURY AND MANGANESE. 

Mercury. 

California Mines. — Mercury, or quicksilver, is found in 
paying quantities in but one district of this country, and 
here, as indeed throughout the world, the universal ore is 
the sulphide cinnabar, with which native mercury and some 
other ores are found in minor quantities. In this coun- 
try, which for a long time held second place as a mercury- 
producer, but three states have ever supplied any of this 
metal ; and of these, California is the only important one, 
the other two, Oregon and Utah, having had a small out- 
put for a short time only. Ores of mercury have been found 
in Nevada, New Mexico, and elsewhere; but, although it 
is highly desirable to have new mines, none of them have 
proved important. 

It is noteworthy that a metal so important in gold 
miniDg should have been discovered in California at about 
the same time that gold was found there. In 1845 the 
occurrence of mercury was noticed, and when gold min- 
ing began, this metal was at hand in such abundance that 
California soon took second place in the quicksilver pro- 
duction of the world. The mercury of California occurs 
in a belt of metamorphic rocks, and in these a number of 
mines have been opened, the most famous being the New 
Almaden and the New Idria. These mines have decreased 

253 



254 ECONOMIC GEOLOGY OF THE UNITED STATES. 

their output of late years, but, as some others are increas- 
ing, the total output of the state in the last year or two 
has not decreased, although in fifteen years there has been 
a decrease to about one-third of the output at the beginning 
of this period. 

At New Almaden 1 cinnabar is found in two fissures which 
unite below, enclosing a wedge-shaped mass of rocks, chiefly 
slates. Running nearly parallel with this, and a short dis- 
tance away, is a dike of rhyolite, which is of recent age, and 
probably the cause of the quicksilver deposit. The cinnabar, 
which contains some metallic mercury, occurs in a gangue 
of dolomite, calcite, and quartz, containing also iron pyrite. 
There is apparently no substitution or replacement, but the 
ore has been deposited in cavities and has, at times, impreg- 
nated the porous rocks through which the fissure passes. 
Already the mine is below the 1800-foot level, and at this 
depth a temperature of 88° is encountered, which indicates 
that the volcanic heat is not yet entirely gone. 

The New Idria mine, of the same state, does not illustrate 
any new point, but the ore occurs there in sandstones. A 
third important mine of the same region is the Sulphur 
Bank, which was first opened as a sulphur mine and later 
developed for mercury. This is an extremely interesting 
mine, since the vein is of very recent date, and, indeed, is 
apparently not yet finished. A fissure, filled with brecciated 
fragments, crosses sandstone, shale, and a capping of augite 
andesite, and in this the cinnabar serves as a cement to the 



1 A description of this mine will be found in the volume of the Eleventh 
Census upon Mineral Industries, pp. 202-245. Becker's Monograph XIII. 
U. S. Geol. Survey, 1888, entitled Geology of the Quicksilver Deposits of the 
Pacific Coast, contains a very complete description of these deposits. 



MERCURY AND MANGANESE. 



255 



breccia, at times impregnating the porous walls. Hot 
water still enters the vein, and it appears that the mineral 
deposition is still in progress, although the greater part of 
the work is done. 1 The silica at present being deposited is 
still soft. Other mines are found in this same district, and 
some of them were opened in the early fifties. The old veins 
are practically exhausted and must apparently be abandoned 
soon, but new ones of promise have been recently opened. 

The following table shows the production of the five 
largest mines since 1850 : — 



PRODUCTION OF CALIFORNIA MINES. 
Flasks (76^ Lbs.). 



Mines. 


1850. 


1855. 


1860. 


1865. 


1870. 


1875. 


1880. 


1885. 


1890. 


1891. 


New Almaden . . . 


7,723 


29,142 


7,061 


47,194 


14,423 


13,648 


23,465 


21,400 


12,000 


8,200 


New Idria .... 






2,000 2 


5,000 2 


9,888 


8,432 


3,209 


1,144 


977 


792 


Eedington .... 








3,545 


4,546 


7,513 


2,139 


385 


505 


442 


Sulphur Bank . . . 












5,372 


10,706 


1,296 


1,608 


3,429 


Napa Consolidated 














4,416 


3,506 


1,375 


4,454 



Foreign Mercury Mines. — The most important quicksilver 
deposit in the world is in the Almaden mine of Spain, which 
has been worked since prehistoric times. Strabo speaks of 
it, and Pliny states that 10,000 pounds came from there to 

1 Phillips' Ore Deposits, pp. 68, 73, and 559 ; Becker's Monograph (referred 
to above), and articles by Le Conte in the American Journal of Science as fol- 
lows : Vol. XXIV., 1882, pp. 23-33 ("The Phenomena of Metalliferous Vein 
Formation now in Progress at Sulphur Bank, California," Le Conte and Ris- 
ing); Vol. XXV, 1883, pp. 424-428 ("On Mineral Vein Formation now in 
Progress at Steamboat Springs," etc.); Vol. XXVI., 1883, pp. 1-19 (" Genesis 
of Metalliferous Veins "). 

2 Estimated. 



256 ECONOMIC GEOLOGY OP THE UNITED STATES. 

Rome, each year, it being worked by condemned criminals, 
who were probably slowly killed by mercurial poisoning, 
from which miners in almost all mercury mines suffer. 
Although worked for such a long period of time, the mine 
is not as deep as the New Almaden, for it has not gone far 
below 1000 feet. In the mine a temperature of 90° 
is encountered. The ore is cinnabar, with some native 
mercury, occurring in bunches and veins, in a quartz gangue 
containing also iron pyrite and galena. Whether it is a true 
fissure vein or an ore channel is not determined. There are 
three nearly parallel veins, sometimes twenty feet wide, 
separated by thin bands of slate from two to three feet in 
width, and in the lower levels the deposit is worked as a 
single vein. The country rock is Upper Silurian slates and 
limestones underlain by a mass of diorite, which is probably 
the cause of the deposit. 

The following table gives the output from this mine since 
1850, the statistics from 1850 to 1870 inclusive being ap- 
proximate estimates : — 

PRODUCTION OF THE ALMADEN MINE. 

Flasks (76| Lbs.). 

1850 20,000 

1860 24,000 

1870 32,000 

1880 41,640 

1890 50,202 

1891 47,993 

The Idria mine, in Austria, is in Jura-Trias conglomerates, 
sandstones, and slates, which are locally impregnated with 
cinnabar. By far the greater part of the ore comes from 
bituminous slates, where it occurs in irregular pockets be- 



MERCURY AND MANGANESE. 257 

tween large areas of barren rock. Calcite, quartz, and pyrite 
also occur. The strata are tilted in places to a nearly vertical 
position, though not always at such a steep angle, and they are 
crossed by fissures. Since the mines grow richer as the depth 
increases, it is supposed that the source is from below, per- 
haps from some hidden mass of igneous rock. This mine 
has been steadily increasing its output, from 4100 flasks in 
1850 to 15,000 flasks in 1891. 

Quicksilver comes also from Italy and from Russia. In 
the latter country there is a single mine in the province of 
Ekaterinoslav, which began to produce in 1887 ; but little 
is known of this mine, excepting that the ore is cinnabar. 
Other mercury mines have been worked in Russia in the 
past, and the discovery of new deposits is announced, but our 
information concerning them is very limited. A mercury 
mine is also situated in Servia, and from this source about 
a thousand flasks a year are produced. A cinnabar mine in 
the Palatinate, in Germany, was of importance from the 
fifteenth to the eighteenth century, but no ore is produced 
from there now. It was found impregnating slate strata 
which were crossed by intrusive melaphyrs. 

Outside of Europe and the United States, practically no 
quicksilver is produced, although there can be no doubt that 
veins exist. Some comes from Borneo ; and there is a mer- 
cury mine in Peru, the Huancavelica, which was opened in 
1570. Here the ore occurs in slates and sandstones, and the 
way in which it impregnates the rock suggests that it was 
introduced in the form of a vapour. Of the Peruvian mines 
Bullman says : 1 " Ores of mercury are abundant, but the 
mines have been abandoned, or only worked spasmodically, 

1 The Mineral Industry, Rothwell, 1892, p. 563. 



258 ECONOMIC GEOLOGY OF THE UNITED STATES. 

for a number of years. The most celebrated of the mines is 
that of Huancavelica, which was discovered in 1570, and up 
to 1790 yielded, according to Castelnau, 104,045,200 pounds 
of metal, worth $67,629,380, upon a gross expenditure of 
$10,587,000. The discovery of this great mine was of the 
utmost importance, as it rendered possible the enormous out- 
put of the Cerro de Pasco and Cerro Potosi silver mines." 
Quicksilver is used in the extraction of this silver. In 
Mexico, mercury has been discovered in a number of places, 
but no large amounts have ever been produced. The ore is 
cinnabar, and occurs in limestones and slates, the Guadalcazar 
mines occurring in the former. 

Origin of Mercury. — There is a marked uniformity in the 
ores of mercury, the sulphide being the almost universal ore 
unless it is decomposed to native mercury. A striking asso- 
ciation of quicksilver deposits with slates, sometimes lime- 
stones, is also noticed ; but this seems to be accidental rather 
than a case of cause and effect, for the association is not 
universal, nor is there any apparent reason for the associa- 
tion, unless, possibly, the organic matter in these strata aided 
in the precipitation. There are no reasons for believing that 
the mercury came from these rocks, but some of the sulphur 
may have been furnished by them. In a number of cases, 
the relation between the veins of mercury and neighbouring 
igneous rocks is such that one is forced to conclude that they 
are the cause of the deposits ; and in all cases the position 
of the ore is such that, even though no igneous rock appears, 
it is a reasonable inference to draw that such rocks exist at 
no great depths, having failed to reach the surface, as is very 
commonly the case with these lavas. Mercurial and sul- 
phurous vapours, accompanied, no doubt, by steam, have 



MERCURY AND MANGANESE. 259 

escaped from these igneous rocks by some passage-way, usu- 
ally a fissure, and upon becoming cooler these have been de- 
posited in the vein. Substances so easily turned to gas, when 
heat is applied, as the two elements sulphur and mercury, 
we can readily imagine to be made to adopt this mode of 
accumulation ; and it is interesting to note that the facts in 
the mines support this hypothesis. Becker, Le Conte, and 
others have shown that in the Sulphur Bank and other 
mercury mines, cinnabar is brought up in solution with alka- 
line sulphides and silica, and from this source deposited in 
the veins. Nevertheless there is good reason to still hold 
that the water was charged with these substances from gase- 
ous emanations from volcanic rock. Of primary importance 
in this connection is the peculiar distribution and the rarity 
of the metal. 

Mercury veins appear, therefore, to be in nearly all, if not 
in all, cases, contact deposits of the sublimation type, or indi- 
rectly deposited from a solution of dissolved mercury of this 
origin. It is conceivable, however, that, accompanying some 
volcanic eruption, mercurial vapours may become incorpor- 
ated in stratified rocks in a disseminated condition, and later 
be segregated. 

Their distribution is extremely irregular, and only a few 
localities may be expected to contain them ; namely, regions 
of recent volcanic activity. The reason why they do not 
occur more commonly in the neighbourhood of older igneous 
rocks is probably that the heat is too great for their formation. 
An igneous mass of granite, for instance, intruded into the 
strata at a depth of several thousand feet, does not become 
cooled for many thousand years. In the mean time the sul- 
phurous and mercurial vapours cannot condense in the neigh- 



260 ECONOMIC GEOLOGY OF THE UNITED STATES. 

bourhood; but unless they form combinations with other ele- 
ments, there is a tendency for them to migrate from the parent 
mass, and become disseminated instead of accumulated. If a 
fissure 1 is at hand, their escape toward the surface would be 
facilitated, and the conditions for the formation of a vein 
would be present ; but if this is not the case, it is probable 
that the substances become disseminated. Still, it is con- 
ceivable that, under some circumstances, such deposits might 
be formed in the neighbourhood of the plutonic rocks ; but 
speaking generally, the regions of recent volcanic action are 
the seats of quicksilver veins. 

Uses of Mercury. — The most important use of quick- 
silver is in the extraction of gold and silver, by the pro- 
cess of amalgamation, as already described. Its power of 
forming amalgams with other metals makes it of use in the 
arts for the preparation of a substance to be used for sil- 
vering mirrors and for other purposes. The fact that it is 
liquid at ordinary temperatures makes it useful in the manu- 
facture of thermometers ; and this fact, added to its weight, 
renders it of especial value in the construction of mercurial 
barometers. In medicine this metal is used in various forms, 
chiefly as calomel, while cinnabar and other compounds of 
mercury are valuable in the manufacture of pigments. For 
this purpose, it was used by the American Indians and by 
other early races of people. 

The price of mercury, in San Francisco, has varied greatly 
since 1850. In 1850 it averaged 199.45 a flask; in 1855, 
151.65 ; in 1874, 1105.18 ; in 1883, $26.83 ; and in 1892, 138.80. 

1 Available fissures are not liable to occur near intruded masses of igneous 
rocks ; for if they do, the lava will seek them and itself escape as an extru- 
sive rock. 



MERCURY AND MANGANESE. 



261 



Production of Mercury. — The following tables show the 
distribution and variation in supply of mercury. The statis- 
tics for the United States are practically those of California. 
In the table showing the production in the world there are 
no statistics for Borneo, Servia, Russia, Mexico, and Peru ; 
but the total from these places is not great. 

PRODUCTION OF MERCURY IN THE UNITED STATES. 
Flasks (761 Lbs.). 

1850 23,875 

1855 31,941 

1860 10,000 

1865 53,000 

1870 30,077 

1875 50,250 

1877 79,396 

1880 59,926 

1885 32,073 

1890 22,926 

1892 27,993 

The most productive years in this country were between 
1875 and 1881 inclusive ; but since then there has been 
a rapid decline, although, in 1892, owing to the opening 
of new mines, there was an increase in production, making 
the output greater than in any year since 1888. 

PRODUCTION OF MERCURY IN THE WORLD. 
Flasks (76£ Lbs.). 



CotTNTKIES. 


1880. 


1882. 


1884. 


1886. 


1888. 


1890. 


1891. 


Spain .... 


45,322 


46,716 


48,098 


51,199 


51,872 


50,202 


47,993 


United States . 


59,926 


52,732 


31,913 


29,981 


33,250 


22,926 


22,886 


Austria . . . 


10,510 


11,663 


13,967 


15,689 


15,6S9 


15,709 


16,536 


Italy .... 


3,410 


4,060 


7,743 


7,279 


9,831 


13,021 


9,570 


Total . . . 


119,168 


115,171 


101,721 


104,148 


110,642 


101,858 


96,985 



262 ECONOMIC GEOLOGY OF THE UNITED STATES. 

The steady decline of the United States, the general 
uniformity of production of Spain, and the gradual in- 
crease of both Austria and Italy are striking. Chiefly as 
the result of the decrease in output from the United 
States, the mercury supply of the world has suffered a 
decrease, which the increased production of other districts 
has failed to equalize. Should we need more mercury, 
there is every reason to believe that it could be readily 
supplied; but although the gold and silver industries call 
every year for more quicksilver, it must be remembered 
that this demand is not as great as it was fifteen years 
ago, because the reducing works have on hand large sup- 
plies of mercury which have already been used and can 
be used again and again in gold and silver extraction. 

Manganese. 1 

General Statement. — The ores of this metal, of which 
there are a number, are practically all oxides, such as 
pyrolusite, psilomelane, braunite, and wad. Other mineral 
combinations occur, and these are sometimes found with 
the above ores. As a metal, and in its mineralogical asso- 
ciations, manganese is very similar to iron, and this is true 
also of its geological occurrence and distribution. Like 
iron, manganese is widely distributed; but being a much 
less common metal, it is not as frequently accumulated 
into beds. However, when this is done, the ore, in the 
vast majority of cases, is bedded with stratified rocks 

1 A very valuable and complete account of this metal, treated from 
the geological, chemical, and economic standpoints, will be found in the 
report on Manganese, by Dr. R. A. E. Penrose, Jr., Vol. I., Annual Report 
of the Geological Survey of Arkansas for 1890. 



MERCURY AND MANGANESE. 263 

and is frequently associated with iron. In occurrence it 
differs from iron in being less frequently formed by 
replacement; but its common position in the earth is the 
same as that of brown hematite and carbonate of iron; 
namely, either precipitated or concretionary. The marked 
similarity to iron has caused a frequent association of the 
two metals, and a great many of the brown hematites, and 
other ores of iron, are manganiferous. More or less iron 
is usually associated with the manganese and there is some- 
times enough manganese with iron to make the ore a 
manganiferous iron ore. There is every gradation between 
iron oxides and manganese oxides. Manganese-bearing 
zinc ores and manganiferous silver ores are also found. 

Although every state contains them, the actual ores of 
manganese, occurring in economic quantities in this coun- 
try, are limited. Since this metal is extensively used in 
the manufacture of steel, large supplies are mined with 
the iron and never separated. While this applies with 
full force to the ores containing small quantities of this 
metal, it is nearly equally applicable to the manganif- 
erous iron ores, which are exploited, ostensibly as iron 
mines, but are in reality chiefly valuable because of the 
contained manganese. Manganiferous silver ores at Leacl- 
ville, Colorado, are mined for the silver, and the man- 
ganese-zinc ores of Franklin Furnace, New Jersey, are 
also worked for the zinc, but not for the manganese, al- 
though this is produced as a by-product. Aside from these 
sources, practically all of the home supply comes from three 
states, — Georgia, Virginia, and Arkansas. It will be noticed 
that this distribution coincides, in a general way, with the 
iron-smelting region ; and one may confidently believe that 



264 ECONOMIC GEOLOGY OF THE UNITED STATES. 

if other sources are ever needed, they can easily be found, 
Indeed, even in the Appalachian belt there are manganese 
deposits that can be called upon for a supply at any time ; 
and no doubt the metal exists in parts of the far west. 

Manganese in the United States. — There is a manganese- 
bearing belt extending from Vermont to Alabama, skirting 
the old shore line of early Palaeozoic times. This metal 
is found at several points in Vermont, chiefly at South 
Wallingford and Brandon. At the former place the ore 
occurs as nodules, in a clay in Cambrian sandstone, while 
at Brandon it is found in Tertiary strata, probably derived 
from the disintegration of this same Cambrian stratum. 
The New Jersey manganiferous zinc ores are apparently in 
the same belt ; and a deposit of very little value is found, 
in a similar position, in Lehigh County, Pennsylvania. On 
the western slope of the Blue Ridge, chiefly in Virginia 
and Georgia, the most important manganese deposits of this 
belt occur, although the other states have produced some. 

In Virginia there are a number of districts, but only one 
is of marked importance. This, the Crimora district, in the 
Shenandoah valley near Waynesborough, has produced about 
140,000 tons of ore since it was first exploited in 1867. The 
ore is principally psilomelane and pyrolusite, in the form of 
nodules, of varying size, irregularly distributed throughout 
a bed of clay. Shafts and open-works are both used in the 
extraction of this and the other American manganese ores. 

From here southwards no important deposits are encoun- 
tered until the Cartersville district of Georgia is reached. 
In this region almost exactly the same mode of occurrence 
is observed. Since 1866 over 60,000 tons have come from 
Georgia, chiefly from this district. 



MEECUEY AND MANGANESE. 



265 



Arkansas also has several manganese districts, but only 
one, the Batesville, in the northern part of the state, 
is important. Practically the same mode of occurrence 
is illustrated here, — a surface clay, the residual prod- 
uct of the disintegration and decay of Silurian limestones, 
through which the manganese was originally scattered in con- 
cretions, pockets, and sheets, in very much the same man- 
ner as the nodules and layers of concretionary flint and 
ironstone occur in chalk and limestones (Fig. 25). By this 




Fig. 25. — Diagram illustrating the origin of the manganese deposits of Arkan- 
sas, d, non-manganiferous limestone; c, manganese-bearing limestone; b, 
disintegrated limestone; a, residual clay with manganese concretions con- 
centrated. (Modified from Penrose.) 



decay the manganese has been concentrated, and the deposit 
is rendered valuable by reason of this as well as by the 
change in the nature of the enclosing rock from hard 
limestone to soft clay. The ore is irregularly distributed, 
and it is mined by open-works chiefly. Since 1850, 40,000 
tons of ore have come from this deposit, and nearly all 
of this has been obtained since 1880. 

None of the other states are of marked importance, al- 
though Wisconsin and Michigan contain mines of rnanga- 
niferous iron carrying from 2 to 11 per cent of manganese. 
At Leadville, Colorado, manganiferous silver and manganese- 
bearing iron occur, but the latter is of value mainly as a flux 



266 ECONOMIC GEOLOGY OF THE UNITED STATES. 

in silver-smelting and, although some of the manganese is 
saved, most of it is lost. One mine in California has in the 
past twenty-five years produced considerable manganese 
which is chiefly used for local purposes. The ore occurs 
in the metamorphic Cretaceous rocks of the Coast Range, 
and, since 1867, about 10,000 tons of ore have been produced. 
Penrose describes 1 an interesting manganese deposit, which 
is, however, of no economic importance, occurring at Gol- 
conda, in northern Nevada. The ore, which is an impure 
oxide, is in a lenticular bed in a breccia cemented by calca- 
reous tufa. Both the tufa and the manganese are evidently 
precipitated from lake waters in a basin from which the 
water has been evaporated. Many springs contain manga- 
nese, and since near this deposit there are hot springs 
charged with oxide of manganese, Penrose suggests that 
this may have been the source. Manganese spring waters 
entering the lake near this point furnished the water with an 
excess of the oxide of manganese, and this was precipitated 
after the manner of bog iron ore. 

Foreign Manganese Mines. — Canada annually produces a 
small amount of manganese, chiefly from New Brunswick 
and Nova Scotia, on the Bay of Fundy, where it occurs in 
Lower Carboniferous strata. At first the ore was obtained 
from clays and other products of disintegration of the strata ; 
but, this source being exhausted, the mines are now in the 
rock, where the manganese is distributed very irregularly, 
in bunches and seams parallel in general to the stratification, 
and probably of concretionary origin. In the eastern part 
of Cuba, several mines of manganese occur in clays, the ore 
being very rich pyrolusite and psilomelane, often containing 

1 Journal of Geology, Yol. I., pp. 275-282. 



MERCURY AND MANGANESE. 267 

as high as 56 per cent of manganese, and it is claimed that 
large beds of this ore exist in the several mines. The 
present output is shipped to this country. The only other 
manganese-producing country of the American continents is 
Chili, where vast deposits are said to exist ; but, owing to 
the difficulties of transportation, they are not fully developed. 
Moreover, there is no local demand for the ores, and they 
must be shipped abroad. No manganese was produced in 
Chili before 1881, and until 1885 very little was obtained. 
Of the three important districts only one, Carrizal, produces 
manganese at present, and this was not discovered until 1886. 
No geological description of the region is available, but it is 
known that the extensive deposits outcrop at the surface 
like beds or dikes. Whether these are true beds or veins 
cannot be stated, but the former seems more probable. Out- 
side of Europe, New Zealand and Australia are the only 
other notable manganese-producers. 

Europe is by far the most important continent in the produc- 
tion of manganese, and nearly every country produces some 
of this metal. Russia outranks all other countries in this 
respect, and there the ores are found chiefly in the Caucasus 
mountains. Little is known of these deposits, but Phillips 
states that the ore is pyrolusite in Miocene sandstone. In 
Great Britain manganese occurs with iron, both brown hema- 
tite and carbonate, and sometimes alone, as in Merionetshire. 
Here the ore is found in a volcanic ash, having been derived 
from the feldspar and accumulated in little veins and pockets 
in the mineralogical form of pyrolusite and psilomelane. 
It would be tedious to describe the occurrence in the other 
European countries, since there is a monotonous uniformity. 
France, Sweden, Portugal, Spain, Italy, Turkey, and other 



268 ECONOMIC GEOLOGY OF THE UNITED STATES. 

countries all produce some. In most cases the ore is bedded 
and concretionary, and strata of all ages from the Cambrian 
to the Tertiary contain it. In the Harz Mountains, in 
Germany, this metal is obtained from small veins in a 
porphyry, in Italy from volcanic tufa, but usually the oc- 
currence is in the sedimentary rocks. 

Origin of Manganese. — The ore deposits of this metal 
may occur in almost any kind of rock, although limestone 
and clay strata are the most common associates. No par- 
ticular geological age can be said to be manganese-bearing, 
but, in this country, the most important source is the older 
Palaeozoic strata. Manganese, in one form or another, occurs 
in nearly all rocks, for it holds the fifteenth place in order of 
importance of rock-forming elements, and is one of the com- 
mon metals. It is more abundant in igneous than in other 
rocks, and this is undoubtedly the original source. Many 
minerals contain it in small quantities, and in many others it 
is an important element in the chemical composition. There 
are several score of minerals in which manganese forms an 
essential part, and some of them are quite common. These 
minerals exist in greater or less quantities in the metamor- 
phic and igneous rocks, and by the decay of these their prod- 
ucts find their way into the stratified rocks, either directly 
as sediment, or indirectly from solution in water. The pres- 
ence of manganese is frequently shown by a brown or black 
stain, and the fern-like crystal form of one of its ores, known 
commonly as dendrites, is very common. 

Since the metal is very much like iron in chemical be- 
haviour, we find it occurring under the same general con- 
ditions. Water takes it into solution and precipitates it in 
the same manner that bog-iron ore is precipitated. It may 






MERCURY AND MANGANESE. 269 

be gathered into regular layers, or it may be disseminated 
through the strata. If the latter is the case, it may, under 
favourable conditions, be gathered together at a later period, 
into beds and concretions of manganese in the same way 
that iron ores are gathered together to form ironstone 
concretions. Being less abundant and less valuable than 
iron, this ore cannot ordinarily be mined when found in this 
condition ; and, indeed, the same is true of much of the iron 
found in the same mode of occurrence. For successful min- 
ing, the ordinary manganese must be concentrated still more ; 
and this has been done by nature, in many places, by the 
decay of the enclosing rocks and the removal of the soluble 
parts. Manganese ores, being less soluble than many of the 
minerals formed by this decay, remain behind with the 
residue in residual soil, and are naturally more concentrated 
by the removal of some of the enclosing minerals. Practi- 
cally all of the manganese mined in this country comes from 
this source, and in other countries considerable supplies are 
found in the same condition. Often, however, the final 
stage of concentration has been omitted, and the mines are 
in the rock itself ; but this is possible only where the ore is 
very pure, or abundant, or easily and cheaply exploited. 

Thus there are three stages in the formation of most man- 
ganese deposits, and to these, in many cases, a fourth is 
added. These are : first, derivation from the decay of crys- 
talline rocks (metamorphic and igneous) ; secondly, deposi- 
tion in the stratified rocks ; thirdly, concentration into nod- 
ules or concretions ; fourthly, a still further concentration 
by the decay of the enclosing rocks and the formation of a 
residual soil; In some cases the ore may be sufficiently con- 
centrated at the time of actual deposition, as in the Gol- 



270 ECONOMIC GEOLOGY OF THE UNITED STATES. 

conda deposit of Nevada; and in others, as in the Harz 
Mountains, the ore may be derived and directly deposited in 
veins in the igneous rocks which furnish the manganese. 
These, however, may be considered exceptional deposits. 

Uses of Manganese. — Before the beginning of the Chris- 
tian era the ores of this metal were used as a colouring for 
glass, and even at present this is an important use of the 
oxides. Pure pyrolusite is used to colour glass and also pot- 
ter}^, producing the various shades of violet, purple, brown, 
and black. An excess of manganese produces the jet-black 
commonly seen in door-knobs, while a slight amount gives 
violet, and intermediate amounts purple and brown. Much 
also depends upon the degree of heat used in the process. 
The ores of manganese also act as decolourizers, and their 
introduction into ordinary glass corrects the green colour 
given by iron. Only pure ores are useful for these purposes, 
and the greater part of our supply is too impure to be of use 
in the industry of glass-making. 

Until recently the most important use of the manganese 
ores was in the manufacture of chlorine and bromine, the ore 
acting as a carrier of oxygen. For bleaching, in the manu- 
facture of disinfectants, as a drier in varnishes, in the print- 
ing of calico, and for other purposes, manganese is in common 
use; but at present more than nine-tenths of the ore mined 
is used in the manufacture of iron and in alloys. In steel- 
making two forms of manganese-iron alloy are used, — Spie- 
geleisen, in which 25 per cent or less is manganese, and 
ferro-manganese, in which the amount exceeds 25 per cent. 
These terms are, however, used variably, and the percentage 
of the metals in the alloy varies greatly. The effects pro- 
duced on the iron are very important, but intricate. It pre- 



MERCURY AND MANGANESE. 



271 



vents the formation of gas cavities during the solidification 
of the steel, restores carbon, carries off oxygen, and produces 
other valuable effects. 

The price of manganese varies so greatly with its richness 
and purity, and with the purpose for which it is adapted, 
that no figures of value can be given without entering into 
details. The value of the ore varies from eight to ten dollars 
a ton, being usually between nine and ten dollars. 

Production of Manganese. — The following tables illustrate 
the distribution of the manganese output of the world stated 
in tons of ore : — 

PRODUCTION OF MANGANESE ORE IN THE UNITED STATES. 
Long Tons (2240 Lbs.). 



States. 


1880. 


1882. 


1884. 


1886. 


1888. 


1890. 


1891. 


1892. 


Arkansas . . 
Virginia . . . 
Georgia . . . 
Colorado . . 
California . . 
Vermont . . 


3,661 
1,800 


1T5 
2,892 
1,000 


800 
8,980 


3,316 

20,567 

6,041 


4,312 
17,646 
5,56S 

1,000 


5,339 

12,699 

749 

6,397 

386 

none 


1,650 

16,248 

3,575 

964 

705 

49 


6,000 
5,000 
2,000 

none 


Total . . . 


5,761 


4,532 


10,180 


30,193 


29,19S 


25,6S4 


23,416 


17,000 


Value . . . 


$86,415 


$67,9S0 


$122,160 


$277,636 


$279,571 


$219,050 


$239,129 


$170,000 



Besides the above a few tons come annually from other 
states, but this does not materially affect the total. The 
marked decrease since 1886 in all the districts, excepting 
Arkansas, is a noteworthy feature of this table. The total 
for the United States shows a rapid increase, which in 1887 



272 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



reached the highest point (34,524 tons), since which time it 
has strikingly decreased. In thirty years the manganese 
output of the United States has amounted to 300,000 tons. 
Since the annual consumption is about 50,000 tons, the coun- 
try produces much less than half the amount consumed. 
Cuba, Chili, and Russia are the chief foreign sources of our 
manganese. 

In 1889 Michigan produced 81,341 tons of manganiferous 
iron, and Colorado 2075 tons, valued at about |3.25 a ton. 
Colorado produced 64,987 tons of manganiferous silver ores 
valued at $3.50 a ton ; and the New Jersey zinc ores pro- 
duced 43,648 tons of manganese residuum valued at $1.25 a 
ton, from which 14,124 tons of spiegeleisen were produced. 

PRODUCTION OF MANGANESE ORE IN THE WORLD. 
Metric and Other Tons. 



Countries. 


1881. 


1883. 


1885. 


1887. 


1889. 


1890. 


1891. 


Russia 1 


11,224 


17,029 


60,458 


58,135 


77,937 


182,346 


190,0002 


Chili 3 






4,041 


47,521 


28,683 


47,986 


34,462 


United States 1 


4,974 


6,255 


23,637 


35,087 


24,592 


26,103 


23,898 


Cuba 










4,000 


21,810 


21,987* 


Great Britain x 


2,931 


1,308 


1,716 


14,000 


8,997 


12,646 


9,632 


Sweden 1 








8,659 


8,645 


10,698 


9,079 


Turkey 










8,000 






Portugal 










5,000 






Italy 1 






1,802 


4,434 


2,203 


2,147 


2,429 


Canada 1 








1,130 


1,320 


1,205 


249 



The above table is approximate only, since accurate statis- 
tics cannot be obtained. Marked fluctuations in the output 



i Metric tons (2204 lbs.). 
3 Long tons (2240 lbs.). 



2 Estimated roughly. 
4 Exported. 



MERCURY AND MANGANESE. 273 

are noticed, showing that the industry is more or less un- 
stable ; but the most striking feature of the table is the rapid 
increase in production of Russia and Chili. In 1888 the total 
production of the world was about 153,000 tons; in 1889, 
about 160,000 tons ; and in 1891, approximately 300,000 tons, 
this increase being chiefly due to Russia and Chili. 



CHAPTER XII. 

TIN AND ALUMINUM. 

Tin. 1 

General Statement. — A single ore, the oxide cassiterite, 
is the source of this metal ; and it, more than any other 
equally common metal, may be said to have a typical mode 
of occurrence. It is found in place, in coarse granite, or in 
rocks immediately associated with such a granite, and excep- 
tions to this are extremely rare. Being heavy and non- 
destructible, tin oxide accumulates in placer deposits, exactly 
as does gold and platinum ; and nearly all of the actual tin 
mines in the world have been discovered by first finding 
stream-tin and then tracing the ore to its source. The 
greater part of the tin supply of the world is obtained from 
gravels, but there are also many mines in the rock. 

In distribution, this metal occurs throughout the world, 
usually wherever granite is found ; but paying tin deposits 
exist only where the ore is concentrated in river gravels or, 
under particularly favourable conditions, in the bed rock. 
Therefore tin mines are widely scattered, but comparatively 
rare. There are none in the United States which are at 

1 A very complete description of tin mines and mining is found in Koth- 
well's Mineral Industry for 1892, pp. 439-462. A description of the occur- 
rence and methods of obtaining tin in the Straits Settlements is found in the 
volume on Mineral Industries, Eleventh Census, pp. 257-264. The Cornwall 
and Devonshire mines are fully described in Phillips' Ore Deposits, pp. 
110-154. This description of tin is mainly abstracted from these sources. 

274 



TIN AND ALUMINUM. 275 

present producing; but this industry is an exceptional one; 
for, although none of the metal is produced, many per- 
sons are employed in mining for tin. 

Tin Mines of the United States. — This metal has been 
found in nearly all the states of the Union where granite 
occurs. Thus cassiterite has been found in the New England 
and southern Atlantic coast states and in the Cordilleras, 
but ordinarily in such small quantities that even develop- 
ment is not deemed worth undertaking. Some shafts have 
been constructed, but so far without bringing any returns 
worth considering. Serious developments of tin mines have 
been made in Virginia, where for a number of years stream- 
tin was found sparingly in the gold-bearing gravels. On the 
western slope of the Blue Ridge, in the Shenandoah valley, 
tin was found in place, in 1880 ; and since then much work 
has been done in the development of this property, which 
promises well. Here the cassiterite is found in small veins 
and in grains, and even nodules a foot or more in diameter, 
occurring in a coarse-grained granite. The ore also occurs 
here in quartz veins, associated with wolframite, beryl, and 
other minerals typical of tin veins. At about the same time 
that cassiterite was discovered in the Virginia granite, its 
presence was also noticed in North Carolina, where the ore 
is found in very nearly the same mode of occurrence as in 
the Black Hills. Cassiterite is also found here as stream-tin, 
but neither of these deposits has proved of value as yet. 
Alabama contains tin ore in stream gravels and also in a 
coarse gneiss. 

The most famous tin-bearing region in this country is that 
of the Black Hills, where, in 1883, cassiterite was found in 
place in a coarse-grained granite intruded into slates and 



276 ECONOMIC GEOLOGY OF THE UNITED STATES. 

schists. Its occurrence was noticed many years before this 
in the auriferous gravels of that region. Here the ore occurs 
disseminated in the' granite and in veins of pegmatite, which 
are composed of quartz and mica in coarse crystals. A large 
number of mining claims have been located in this district, 
chiefly in and near Harney's Peak, and several mines have 
been opened and extensively developed ; but up to the pres- 
ent time they have not sold any tin. Immense sums of 
money have been expended by companies with a large capi- 
tal, and recently reduction works have been built. These 
facts indicate confidence, on the part of the managers, that 
the tin deposits will soon begin to bring profitable returns ; 
but, notwithstanding this, it is the opinion of many compe- 
tent American mining engineers that, with the existing con- 
ditions of inaccessibility, high price of materials and labour, 
these tin mines cannot be made to profitably compete with 
the more easily worked deposits in other parts of the world. 
If this is really true, and there seems good reason to be- 
lieve that it is, large sums of money have been extrava- 
gantly and foolishly wasted in development. The next few 
years will witness either a large output from these mines or 
a collapse of the enterprise. 

In California, tin has been known to exist, in some of the 
auriferous gravels, ever since their discovery; and since 1868 
tin mining has been carried on intermittently near Riverside, 
on the San Jacinto land grant, but since September, 1892, 
this mine has been closed. It is practically the only tin 
mine in this country which has so far produced marketable 
tin. Prior to 1892, about 120 tons of this metal have been 
produced, and since then, to the time of suspension of opera- 
tions, about 140 tons were obtained. A striking resemblance 






TIN AND ALUMINUM. 277 

is noticed between the mode of occurrence of the tin of this 
region and that of Cornwall, England ; for, in both cases, there 
is a granite mass cutting slates, and both of these rocks are 
traversed by quartz-porphyry dikes. All three of the rocks 
contain tin, but the most promising vein is in the granite. 
Associated with the ore are tourmaline, quartz, feldspar, and 
other minerals, and the tin is sometimes in veins, sometimes 
disseminated. Taking everything into consideration, this 
was considered, a few years ago, the most promising tin 
region in the country, but the fact that it has been closed, 
after a careful examination of its possibilities, indicates that 
it is not a profitable deposit. Indeed, it may be said that the 
United States does not at present show any distinct promise 
of producing tin. Lodes which might be worked in other 
countries are not uncommon, but the value of labour is so 
high that they cannot be developed, and so far the country 
has produced no "tin bonanzas." It is true that prospectors 
generally do not know tin ore from some of the iron ores, 
and there are, possibly, valuable deposits at present undis- 
covered. 

Foreign Tin Mines. — Cornwall, in England, is the most 
famous tin region of the world, and this metal has been, 
produced from there for at least two thousand years. At 
first the cassiterite came from stream gravels, but now all 
the tin is obtained from mines. The principal sources are 
granite cutting slates, the slates themselves, and quartz- 
porphyry dikes which have been intruded into both of these. 
Associated with the tin are ores of copper, blende, and 
galena, as well as quartz, feldspar, mica, tourmaline, topaz, 
wolframite, etc., and the character, and even the kind, of ore 
varies from one rock to another. The veins are frequently 



278 ECONOMIC GEOLOGY OF THE UNITED STATES. 

of the segregation type, crossing all rocks and sending out 
offshoots, often in such intricacy that a complete network 
of veins is formed. There is also a great variation in the 
width of these veins, for sometimes they decrease even to 
a mere line and then swell to a width of many feet. A 
peculiar mode of occurrence is noticed at St. Ives and else- 
where, where " carbonas " occur, these being large lenticular 
masses of granite impregnated with tin, and sloping away 
from the nearly vertical " parent vein." There seems to be 
a considerable variety in the occurrence of the tin; for at 
times the veins are apparently fissure veins, again segregation 
and often impregnation deposits. 

Next to Cornwall, Devonshire has been the most impor- 
tant tin-producing region of England, but at present this 
source appears to be exhausted. Here the occurrence is 
very similar to that at Cornwall, but no quartz-porphyry is 
present. In the eleventh and twelfth centuries Devonshire 
produced more tin than Cornwall ; but while the former 
has gradually decreased its output, Cornwall has shown a 
steady increase, from an average of about 300 tons a year in 
the thirteenth century, to over 9000 tons in 1891. During 
a period of 690 years, it is estimated that the two dis- 
tricts have together produced 1,128,000 tons of tin ; and 
of this, not much more than 100,000 tons came from 
Devonshire. 

Elsewhere in Europe tin is not abundant, but it is mined 
in a number of countries. In France it is found in Brittany, 
where the geology very closely resembles that of Cornwall. 
The Erzgebirge region in Germany has tin in granites cut- 
ting crystalline schists, and in very nearly the same associa- 
tion as in Cornwall. This same tin-bearing belt extends 



TIN AND ALUMINUM. 279 

into Bohemia, in Austria, where, at Schonfeld, tin was mined 
as long ago as the time when fire setting was used for min- 
ing in place of tools. In 1355 this was an important district. 
Cassiterite is found in granite in Finland ; and in Spain tin 
mines were worked by the Phoenicians in quartz lodes in 
slates and schists, but they are not now productive. During 
the reign of Agricola, Portugal produced stream-tin, and in 
this country tin is also found in the granite. 

By far the most important tin-producing district at the 
present time is that of the Straits Settlements. For at least 
four hundred years this metal has been exported from there, 
and it is possible that this was the source of the tin used in the 
manufacture of the early and prehistoric bronze. In the state 
of Perak, on the Malay Peninsula, tin has been obtained for 
at least a century. Granites, slates, and other rocks consti- 
tute the mountains of the region, and cassiterite is known to 
occur in the granite, although this source is not explored or 
worked. At present the tin produced comes entirely from 
a small area not exceeding twenty square miles, and from 
here two-thirds of the output of the Straits Settlements is 
obtained. Associated with the cassiterite in the gravels are 
water-worn fragments of granite and tourmaline, which 
show that here also the uniform geological and mineralogical 
association, noted above, is preserved, although it is said 
that tin has also been discovered in place in veins crossing a 
limestone. The methods of mining are extremely crude, the 
work being performed by Chinese and natives, but the Amer- 
ican process of hydraulic washing is about to be introduced. 

On the neighbouring islands of Banca and Billeton the 
occurrence of tin is the same as in Perak, since these are 
practically continuations of the same area. Here some 



280 ECONOMIC GEOLOGY OF THE UNITED STATES. 

mining has been carried on in the bed rock. Tin is also 
fonnd in the gravels of Sumatra and Burmah, and it is prob- 
able that other sources of this metal will be found in the 
gravels of other East India islands. If necessary, the output 
from these several districts could be greatly increased, and 
it is probable that when these superficial deposits are ex- 
hausted, as they must be before a great many years, a 
more permanent but less profitable supply will be found in 
the neighbouring bed rock. 

Australia is also an important source of this metal, the 
stream-tin having been noticed soon after the discovery of 
gold in both Victoria and New South Wales. Every coun- 
try of this continent has produced some tin, but the only 
important regions are in New South Wales and Queensland. 
The source of the ore is the Australian Cordilleras, where it 
exists, chiefly in granite, in geological association very simi- 
lar to that of Cornwall. At present, however, these sources 
are barely explored, the greater part of the supply being 
obtained from the gravels. The mode of occurrence and 
origin of the stream-tin is the same, in general, as that of 
the gold with which it is associated. Even the gravels 
which are buried beneath lava flows are tin-bearing. Vic- 
toria also produces some tin, and in Tasmania a rather 
unique occurrence exists, the ore being found there in a 
eurite-porphyry which traverses slates. Vast stores of this 
metal exist in Australia, both in unworked gravels and 
granites, and this region will undoubtedly long continue an 
important source of tin. 

In South America the only important tin district at pres- 
ent exploited is in Bolivia, where it has long been known to 
exist, although hitherto very little has been produced, ex- 



TIN AND ALUMINUM. 281 

cepting as a by-product in silver mining in the Potosi dis- 
trict. Recently, by the construction of a railway, the tin of 
this section has become valuable, and the output will no 
doubt increase. The silver-tin deposits occur in a porphyritic 
diorite, intruded into sandstone, and also in a trachyte cut- 
ting slates. Mexico also produces tin, and in the state of 
Durango the cassiterite occurs in veins in porphyritic tra- 
chyte. For many years stream-tin has been produced in 
small quantities by natives, but the output is not important. 

Origin of Tin Ore. — The noticeable features concerning 
tin are the marked uniformity in character of the ore and 
the singularly uniform association with igneous rocks, par- 
ticularly with granite. Other igneous rocks, such as eurite, 
diorite, and trachyte porphyry, are stanniferous in some cases, 
but ordinarily the association is with granite. A study of 
the Cornwall mines shows that these deposits are not of con- 
tact origin, nor are they contemporaneous with the intrusion 
of the granite, as one might at first suppose, for they are 
found also in quartz porphyries which have been intruded 
into the granite since it solidified. One is, therefore, driven 
to the conclusion that these deposits have been derived 
by subsequent concentration, and their nearly constant 
association with granite points to this as the common source. 
In some cases the process of concentration is akin to that 
of segregation, but frequently the metal occurs in true veins. 

Notwithstanding these contradictory facts, it seems very 
probable that many of the tin deposits are actually of con- 
temporaneous origin with the granite. The position of the 
tin in the rock, the association with tourmaline, and other 
facts, point to this conclusion. Indeed, it is not improbable 
that some of the coarse granitic or pegmatite veins are them- 



282 ECONOMIC GEOLOGY OF THE UNITED STATES. 

selves actual intrusions and the source of the tin. The 
genesis of the ore has not been determined, in spite of the 
apparent simplicity of occurrence and the great age of the 
mines. Ordinarily the ore is too disseminated for profitable 
mining, and consequently a second stage is generally neces- 
sary; namely, natural concentration in river gravels, which 
are the source of by far the greater part of the world's 
supply of tin. 

Uses of Tin. — The manufacture of bronze and of tin 
plate calls for the greater part of the tin supply, although 
some is used in plumbing and for some minor purposes. 
Bronze has already been described under copper. Britannia 
metal, usually composed of from 82 to 90 parts of tin 
alloyed with antimony and minor quantities of copper and 
sometimes zinc, is used for various purposes in the manu- 
facture of cheap utensils, etc. The manufacture of tin 
plate, which is so useful in tin ware and tin cans, consists 
simply in coating iron with tin to exclude the air and pre- 
vent the iron from rusting. In the United States, and in all 
European countries excepting Great Britain, the tin con- 
sumed is almost entirely imported. This and platinum are 
the only important metals which we find it necessary to 
import extensively. 

In 1892 tin sold at 20 cents a pound; but since 1885 
the price has fluctuated from 16| to 39.95 cents a pound, 
with an average price of a little over 20 cents. These 
fluctuations are due not to variations in supply, but to 
the operations of the syndicates which control the supply. 
The tin and tin plate imported into this country in 1891 
were valued at $33,991,668, there having been a steady 
increase since 1870, when the imports amounted to only 



TIN AND ALUMINUM. 



283 



$9,671,759. Of the total imports for 1891, 125,900,305 
were tin plate and sheet tin. 

Production of Tin. — The following table shows the out- 
put of tin from the leading districts in the world : — 



PRODUCTION OF TIN IN THE WORLD. 
Short Tox\s (2000 Lbs.)- 



Districts. 


1880. 


1885. 


1890. 


1891. 


Straits Settlements . . 
Great Britain .... 
Australia 


20,226 
8,918 
9,177 


25,280 
9,331 

9,088 


38,019 
9,000 
6,415 


42,560 
9,354 
5,991 


Total 


38,321 


43,699 


53,434 


57,905 



Besides these regions, in 1891 about 1550 tons of tin were 
produced in Bolivia, not more than 50 tons in Mexico, 
720 tons of ore in Austria, 75 tons of tin ore in Germany, 
and 57 tons in the United States. In 1892 the United 
States had an output of 65 tons, valued at $29,827. 



Aluminum. 1 
Occurrence of Aluminum. — No metal has, in the last few 
years, attracted more attention than aluminum, which has 
had such a remarkable development that we are hardly 

1 A good account of aluminum, although at present rather old in some 
respects, owing to the rapid progress in production of the metal, will be 
found in Aluminum, its Properties, Metallurgy, and Alloys, Richards, 1890. 

Another account is found in the Eleventh Census volume on Mineral 
Industries, pp. 277-284 ; Mineral Besources of the United States, Day 
(U. S. Geol. Survey), 1891, pp. 147-163; and Rothwell's Mineral Industry, 
etc., 1892, pp. 11-18. 



284 ECONOMIC GEOLOGY OF THE UNITED STATES. 

able to state its present position or predict its probable 
future. Until a few years ago, it was only a chemical 
curiosity comparable with many of the rare metals; but 
now it is already a common metal, pushing its way into 
the arts in competition with the older and well-established 
metals. Before 1827 aluminum was unknown, while, prior 
to 1857, it was a decided curiosity, and it remained of no 
practical importance until a few years ago, when cheap 
processes for its reduction were successfully introduced. 
Aluminum is the most abundant metal and the third most 
common element in the earth's crust. Hundreds of min- 
erals, particularly the complex silicates of alumina, contain 
this metal in essential combinations, and it is present also, 
in smaller quantities, in other minerals. In ordinary clay, 
which is hydrous silicate of alumina, there is an inexhausti- 
ble source of this metal ; but the mineralogical association 
is too refractory for profitable separation with the present 
methods. 

The ores which can be made to give up their aluminum 
easily are very few. Of these, corumdum the oxide, is 
too valuable for abrasive purposes to be used as a source 
of the metal ; diaspore and gibbsite the hydrous oxides, 
are not found in sufficient abundance ; and alumnite the 
sulphate, although found in some places in the west, par- 
ticularly in New Mexico, does not serve as an ore, because of 
the competition of more abundant and available minerals. 
Until recently the chief source of the metal was cryolite, 
the fluoride of sodium and aluminum (A1 2 F 6 , 6NaF), which 
occurs in large quantities in Greenland, from which region it 
has been brought to this country, for a number of years, 
to be used in the extraction of aluminum. Now bauxite 



TIN AND ALUMINUM. 285 

(A1 2 6 H 6 ) is the chief source of this metal, and it is so 
new for this purpose, and has become so important, that 
a detailed description is introduced. 

Bauxite is, in reality, a limonite in which a part of the 
iron has been replaced by aluminum; and the true bauxite 
contains from 50 to 70 per cent of alumina. It was first 
found in the village of Baux in southern France, and was, 
for a time, worked as a source of iron ; but the ore proved 
of little value for this purpose. In mode of occurrence it 
closely resembles limonite, being found both in nodules 
and in an earthy form. The colour of the pure mineral is 
white, however, and the mineral is both soft and granular. 
Bauxite, at the French locality, occurs in limestone, through 
which it is scattered in beds, nodules, and grains, and it is 
believed that it was deposited by precipitation in lakes, simi- 
lar to the mode of formation of lacustrine limonite, and 
later concentrated by concretionary action. Other deposits in 
France, Italy, Austria, and Ireland confirm this view, but 
in some places, particularly in Germany, the mineral is 
evidently derived from the decomposition of basalt. These 
facts point to two probable modes of origin for the Euro- 
pean bauxite. 

In America this mineral is found in Alabama, Georgia, 
and Arkansas ; and when explorations have been carried 
into other regions, particularly the volcanic and lacustrine 
regions of the Cordilleras, there seems to be no reason to 
doubt that extensive deposits will be found. Mining for 
bauxite was begun in Alabama late in 1891, and the first 
shipments were made in 1892. The ore is associated with 
limonites and kaolins, resting on Lower Silurian dolomitic 
limestone of the Knox series; and in Georgia the occur- 



286 ECONOMIC GEOLOGY OF THE UNITED STATES. 

rence is exactly the same, the ore in both cases being 
scattered through clay and near the manganese deposits. 
This mineral may have been concentrated from the decay 
of the limestone, but Dr. Spencer, the state geologist of 
Georgia, considers it a precipitated deposit formed in 
lagoons, the mineral having been derived from the solu- 
tion of portions of decomposed crystalline rocks which exist 
about twenty miles east of there. Recently Dr. Brauner, 
state geologist of Arkansas, has announced the discovery 
of bauxite in large quantities in the Tertiary of Arkansas, 
where it is found near syenite masses, with which it seems 
to be associated in point of origin. 

History and Metallurgy of Aluminum. — In 1807 Sir Hum- 
phry Davy first attempted to obtain aluminum from its 
oxide ; but he was not successful. It was not until 1827 
that ' Wholer was successful in an attempt to separate alumi- 
num by means of potassium, and as a result he obtained a 
fine gray powder. The same chemist obtained the metal in 
globules in 1845 ; and in 1854-1855 Deville, a Frenchman, 
improved upon this method, and invented a process for the 
extraction of sodium at a greatly reduced price (from 2000 
francs to 10 francs per kilogramme). By substituting this 
metal for potassium, the beginning of the industry of alumi- 
num reduction was made, and for thirty years this Deville 
process was used. Deville also introduced the use of elec- 
tricity in the reduction of this metal, but the high cost of 
producing this prevented him from anticipating the present 
electrolytic process. Since 1886 many improvements have 
been made in the process of aluminum extraction, but none 
have been more important than the introduction of electricity 
and the reduction in the cost of sodium by a new process 



TIN AND ALUMINUM. 287 

invented by an American, Castner. A number of patents 
have been issued for electric processes of reduction, and the 
price of the metal has steadily fallen. If this continues, 
aluminum must soon enter the market as a formidable 
competitor of some of the common metals. The remark- 
able progress of the industry can be no better shown 
than by the following table, which illustrates the fall in 
price : — 

COST OF ALUMINUM PER POUND. 

1856, Spring $90.90 

1856, August 27.27 

1886 12.00 

1889 2.00 

1891 90-.75 

1892 .50 

It is not within the scope of this treatise to discuss metal- 
lurgical processes, but it will be of interest to state briefly 
the process by which aluminum is extracted from the oxide 
in the works at Pittsburg, Pennsylvania. 1 The principle is 
that in the presence of a melted fluoride, alumina is decom- 
posed by the electric current, and metallic aluminum lib- 
erated. The ore is fused in a flux of fluoride of aluminum 
and sodium, and a powerful electric current is applied, which 
liberates the aluminum, while the oxygen forms carbon 
dioxide with a series of carbon blocks. The fluorides act as 
vehicles for the alumina. From time to time the metal, 
which sinks to the bottom, is drawn off, and more ore is 
added, so that the process of reduction is practically a con- 
tinuous one. 

1 Extracted from a statement in the Mineral Resources of the United 
States, Day (U. S. Geol. Survey), 1891, pp. 154, 155. 



288 ECONOMIC GEOLOGY OF THE UNITED STATES. 

The Uses of Aluminum. — This metal has been heralded as a 
competitor of iron, copper, and nearly all the common metals, 
but it seems highly improbable that it will ever seriously 
compete with most of these. It has properties which 
fit it for especial uses, for which other metals are poorly 
adapted. Aluminum is beautiful white in colour, and is not 
sensibly affected by the atmosphere, which makes it in this 
respect superior to silver. In malleability and ductility it 
resembles gold and silver, and can therefore be hammered 
into sheets and drawn into wire. Without a great reduction 
in price, it cannot be made to replace iron and copper wire ; 
and the fact that its power of conducting electricity is less 
than that of copper, makes it probable that it will not replace 
this metal in electricity. It has been stated that aluminum 
will rival steel, but this is unfounded, because its tensile 
strength is only about that of cast iron. Therefore, for pur- 
poses which require a high degree of tensile strength, alumi- 
num cannot be used without greatly increasing the bulk ; and, 
since it is unlikely that the price will decrease below that of 
steel, these uses of this metal will probably never be made. 
The strongest point in favour of aluminum, aside from its 
freedom from tarnish and its beautiful white colour, is its 
extreme lightness. These various properties adapt this metal 
to certain uses-, for which it will perhaps replace some of the 
brass, copper, tin, nickel, and the white alloys. Still, the 
position of aluminum must be considered doubtful, although 
nearly every one admits that it has a bright future. 

At present the chief uses of the metal are toys, fancy 
articles, and ornamental work in machinery. An almost 
infinite number of such uses are now made of the metal, 
among which may be mentioned canteens, sword scabbards, 






TIN AND ALUMINUM. 289 

surveying-instruments, race boats, and other purposes where 
lightness is desired. For plumbing it has not yet come 
into use, because of the difficulty of soldering. Alumi- 
num wire promises to be valuable for some purposes, since 
it can be drawn into fine threads and spun, and does not 
tarnish. 

The alloys of this metal have already assumed importance. 
A small amount added to steel increases its value in several 
respects, but primarily by preventing air-holes in the castings. 
There is an increasing demand for aluminum bronze, and for 
different purposes this alloy is made of different proportions 
of the component metals. With 10 per cent of aluminum, 
copper is given remarkable strength, which fits it for pur- 
poses where great tensile strength is required. Copper con- 
taining about 5 per cent of aluminum is capable of being 
worked like steel, and there is reason to believe that this 
may become important. Every year scores of patents are 
granted for different kinds of aluminum alloys, and already 
there are many hundred such patents. Iri a very few years 
these will be tested and their relative importance determined. 

Taking everything into consideration, it may be safely 
predicted, that, if the price of aluminum can be reduced to 
ten or twenty cents a pound, which in the light of the past 
history seems not improbable, innumerable uses, probably 
chiefly in the alloys, will be found for this metal. It may 
take the place of tin, which the world can well spare, since 
it is liable to become exhausted in time, and it may even 
interfere with the value of zinc, particularly with the use 
of zinc in the manufacture of brass. Even some of the uses 
of iron and copper may be replaced by this metal, but there 
need be no fear that it will seriously interfere with the 



290 ECONOMIC GEOLOGY OF THE UNITED STATES. 

demand for the important metals, unless its cheapness 
becomes as marked as its abundance in the earth. Its very 
cheapness will serve to prevent its extensive use in place of 
silver, and, while it may replace nickel for purposes of plat- 
ing, this metal is making for itself a demand in other direc- 
tions for which aluminum can scarcely be made to serve. 
By the introduction of copper-aluminum alloys, both metals 
will probably have their importance increased. This metal 
will undoubtedly assume its proper position in the next 
twenty-five years ; and, without accepting the rather absurd 
claims made by enthusiasts, it seems certain that this will 
be an important and prominent position among metals. 

Production of Aluminum. — The extremely rapid growth 
of the aluminum industry in this country is shown in the 
following table : — 

PRODUCTION OF ALUMINUM IN THE UNITED STATES. 

Pounds. 

1882 none 

1883 83 

1884 150 

1885 283 

1886 3000 

1887 18,000 

1888 19,000 

1889 47,468 

1890 61,281 

1891 168,075 

1892 . .' 294,313 

The value of the aluminum produced in the United States 
in 1892 was $191,303. In 1890 the total amount of aluminum 
alloys used in this country was 171,759 pounds, while Ger- 



TIN AND ALUMINUM. 291 

many, in 1892, used 616,000 pounds of aluminum bronze. 
Switzerland produced, in 1892, 629,420 pounds of aluminum; 
France, 132,000 pounds; and other European nations were 
also heavy producers ; but, since the industry is so recent, 
statistics are not very full nor valuable on this subject. 

The ore bauxite, from which this was obtained, came in 
America chiefly from Alabama, which, in 1891, produced 
3600 tons, and in 1892, 7200 tons, and from Georgia, which 
produced 3300 tons in 1891. In the latter year we imported 
17,936,504 pounds. Baux, in France, produced 20,000 tons 
of bauxite, in 1888, much of which was exported. There 
are no statistics available for the production of foreign 
bauxite. 



CHAPTER XIII. 

MISCELLANEOUS ORES AND GENERAL REVIEW OF THE 

METALS. 

Nickel and Cobalt. 

Mines in the United States. — These two metals occur 
associated, and much of the cobalt is produced as a by- 
product in the separation of nickel from the ore. The ores 
are niccoliferous pyrrhotite, millerite (the sulphide), nic- 
colite (the arsenide), annabergite (the arseniate), and, in 
New Caledonia and also in other places, garnierite a hydrous 
silicate of magnesia and nickel, which is a brittle, apple-green 
mineral. In this country nickel has been found in the nieta- 
morphic rocks of Massachusetts and Connecticut ; but none 
is produced from these states at present, and the same is 
true of a deposit of garnierite which occurs in serpentine 
in North Carolina. A small percentage of nickel and cobalt 
is saved as a by-product in the smelting of the lead produced 
at the mine La Motte in Missouri. Colorado has a non- 
productive nickel-cobalt arsenide and sulphide mine: and, 
in Nevada, the same ores are found at Lovelock's station, 
where a quartz vein, bearing these metals, occurs in an iron- 
bearing band. Although the mines on this vein have been 
developed, very little ore is produced at present. There are 
mines of pyrrhotite in Oregon, and also of garnierite in ser- 
pentine in the same state. None of these mines are at 
present of importance. 

292 



MISCELLANEOUS OBES. 293 

Practically all of the nickel and cobalt of the country 
comes from Lancaster Gap in Pennsylvania, which, until 
a few years ago, was one of the most important mines of 
these metals in the world. From early in the last century 
until 1852, this mine was exploited for copper, but since then 
its output has been chiefly nickel and cobalt. The ore is 
niccoliferous pyrrhotite and chalcopyrite, carrying from one 
to three per cent of nickel and some cobalt. The vein is 
apparently a fissure, or possibly a segregation vein, at the 
contact between mica schist and a wedge or lenticular mass 
of amphibolite. This deposit is fast becoming exhausted, 
and, unless new deposits are discovered, the district will 
soon become non-productive. 

Foreign Mines. — In Europe the most important nickel- 
cobalt-producing countries are Norway and Sweden, where 
niccoliferous pyrrhotite occurs in several places in the 
metamorphic rocks. Although this region at present ranks 
third in the world, and has been a producer of cobalt and 
nickel for many years, it is still of little importance. Austria- 
Hungary, Prussia, and Great Britain all produce small quan- 
tities of these ores, chiefly as by-products in mines of other 
metals, such as those in the Freiberg district, etc. 

The most important mines of nickel and cobalt in the 
world are in New Caledonia, where the ores were discovered 
in 1867, although not worked until 1874. In many parts of 
the colony, garnierite occurs in serpentine, filling cavities and 
little veins in a decomposed clay consisting of chrome iron 
and cobalt-manganese iron. This appears to be a product, 
not of metamorphism, but of later accumulation. Next in 
importance to this region is that of Sudbury in Ontario, 
Canada, which has increased its output at a remarkable rate in 



294 ECONOMIC GEOLOGY OF THE UNITED STATES. 

the past few years. The ore is niccoliferous pyrrhotite and 
chalcopyrite, occurring in Huronian gneisses ; and, as in the 
case of the Pennsylvania mine, which it closely resembles, it 
was at first worked for copper. Very little cobalt occurs here. 
Since all conditions for profitable extraction exist in this mine, 
it promises to control the nickel supply of the world. 

Cobalt is obtained chiefly as a by-product in the produc- 
tion of nickel, but in some places cobalt ores occur singly. 
The manganese-cobalt-bearing clay, associated with the New 
Caledonia nickel, is an instance of this, as is also a cobalt 
glance found in Chili. 

Origin of Nickel and Cobalt. — All of the important depos- 
its of these ores occur in metamorphic rocks, — the sulphides 
and arsenides in gneisses and schists, the magnesian silicate 
garnierite, in serpentine. This latter association is noticed 
in New Caledonia, North Carolina, Oregon, and elsewhere. 
Whether they are a product of metamorphism, — that is, 
segregation deposits of metamorphic origin, — or whether 
they have been derived by a subsequent process of concen- 
tration cannot be definitely stated ; but the constant associa- 
tion with metamorphic rocks suggests the former as at least 
a general, if not a universal, explanation. 

Uses of Uickel and Cobalt. — Until within a year or two 
nickel was so unimportant that the opening of a large mine 
succeeded in closing the smaller ones ; but from this time on, 
the metal promises to grow in importance. There is a certain 
demand for this metal in the manufacture of cheap jewelry, 
particularly watches, for German silver, for coinage, and for 
purposes of plating. The latter use has been steadily in- 
creasing, and the rapid introduction of bicycles has been 
largely responsible for this. But recently the invention of 



MISCELLANEOUS ORES. 



295 



nickel-steel alloy has created a new and very important use 
for this metal. An addition of a small percentage (about 
4 per cent) of nickel to steel gives to it a greatly increased 
toughness and tensile strength. This steel is now being used 
for armour plates, and will probably be introduced into the 
manufacture of propeller shafts and other parts of machinery 
and engines, as well as for gun and cannon barrels. A 
nickel-copper alloy (20 per cent nickel and 80 per cent 
copper) is being used as a casing for the bullets of the small- 
bore guns in use among the European armies. German 
silver, a general name given to a variety of compounds, is 
an alloy of nickel, copper, and zinc. 

Altogether the future of this metal is very bright, and 
there seems little doubt that some of the smaller and un- 
developed mines of this country will soon begin to produce 
at a profit. During 1892 nickel varied in price from 50 to 
60 cents a pound. 

Cobalt is used, in the form of the oxide, in the manu- 
facture of a pigment, the intense and permanent cobalt blue 
which is used in the manufacture of paints, coloured porcelain, 
etc. There are also some minor uses, chiefly in chemistry. 

Production of Nickel and Cobalt. — The following statistics 
illustrate the production and distribution of these metals in 
this country and in the world : — 



PRODUCTION OF 


NICKEL 


IN 


' THE UNITED 


STATES. 






Pou 


NDS. 






1876 










. 201,367 




1880 
















. 233,893 




1885 
















. 277,904 




1890 
















. 200,332 




1891 
















. 120,848 




1892 
















. 96,152 





296 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



The falling-off in production in the past few years is due 
to the exhaustion of the Lancaster Gap mine and the compe- 
tition of the Canadian nickel. In 1891 the United States 
imported 345,286 pounds of this metal. The value of the 
output in 1892 was $57,691. 

PRODUCTION OF NICKEL IN THE WORLD. 
Pounds. 



Countries. 


1889. 


1890. 


1891. 


New Caledonia 

Canada 

Norway and Sweden .... 
United States 


3,045,641 

682,773 
240,222 
217,633 


3,500,613 

1,435,742 

162,742 

200,332 


5,399,800 

4,626,627 

160,000 

120,848 



In addition to the above, Germany, Great Britain, Hun- 
gary, and some other nations produced unimportant quan- 
tities. 

PRODUCTION OF COBALT OXIDE IN THE UNITED STATES. 

Pounds. 

1870 3,854 

1880 7,251 

1891 7,200 

1892 8,600 

At present, about 200 tons of cobalt oxide are consumed in 
the world. In 1888 Chili exported 25 tons of cobalt ores 
(215 tons in 1887), and Prussia produced 33 tons. New 
Caledonia and other countries also produced cobalt; but 
there are no exact statistics, although New Caledonia ex- 
ports from 2500 to 4000 tons of cobalt ore a year. 



MISCELLANEOUS ORES. 297 

Antimony. 

This metal occurs in a number of minerals, but the only- 
important source is the sulphide stibnite. The usual mode 
of occurrence is in quartz veins, either of segregation origin 
or true fissure veins, but there seems to be no general asso- 
ciation of country rock, although slates are often the enclos- 
ing strata. In this country antimony has been found in a 
number of states, but only one, Nevada, is an important pro- 
ducer. Arkansas contains stibnite deposits in the south- 
western part of the state, where it occurs in quartz veins 
parallel to the bedding. In Kern County, California, this 
ore is also found in quartz veins, but none is produced from 
there. Antimony ore exists in Nova Scotia and New Bruns- 
wick, Australia, Borneo, Japan, which is -the chief source, 
and in nearly all the European countries, principally in 
Portugal, Spain, Austria-Hungary, Italy, and France. In 
all of these mines there is a marked uniformity of occurrence, 
although in some of them other ores of antimony are also 
found ; and some, notably those of Australia, are auriferous. 

Antimony is of chief value for the alloys into which it 
enters ; for, although brittle itself, it imparts a peculiar hard- 
ness and toughness to some metals, notably lead. Of these 
alloys the most important is type metal, which is a mixture 
of lead and antimony. Britannia metal, pewter, and Babbitt 
metal (copper, tin, and antimony), all contain antimony, and 
the metal also enters into certain chemical compounds and 
substances used for medicine. It is also used in vulcanizing 
rubber. Although valuable in an alloy of lead, antimony 
makes gold and silver brittle, and even as small an amount 
as one-tenth of one per cent injures copper very seriously. 



298 ECONOMIC GEOLOGY OF THE UNITED STATES. 

The price of antimony varies greatly, since the supplies are 
local and widely distributed. In 1891 the price fell from 19 
to 12 cents a pound on account of rumours of an increased 
supply from Japan. Since these rumours were unfounded, 
the price rose to 16.25 cents in December, but it then fell 
and at several times during the year 1892 sold for less than 
12 cents a pound. 

The following statistics are the only ones accessible. We 
have no statistics for the production of antimony from 
Borneo, Portugal, and France. 

PRODUCTION OF ANTIMONY IN THE UNITED STATES. 

Pounds. 

1880 100,000 

1885 100,000 

1890 257,768 

1891 910,000 

1892 956,000 

The United States in 1891 imported antimony to the 
amount of $313,909, and the value of the metal produced 
by the country was approximately $45,000 at San Francisco. 

PRODUCTION OF ANTIMONY ORE IN THE WORLD, 1891. 

Metric Tons (2204 Lbs.). 

Japan 3200 * 

United States 1000 

Italy 782 

Austria-Hungary 557 

Spain 547 2 

Canada in 1886 produced 603 tons; but since 1888 the 
output has rapidly decreased, and in 1891 only 9 tons were 
furnished. Italy in 1885 had an output of 2887 tons. The 

i Estimated (in 1890, 3173 tons). 2 Exported. 



MISCELLANEOUS OKES. 299 

total production of antimony in the world was probably not 
far from 10,000 tons in 1891. 

Chromium. 

Chromium is not used in the metallic state, but is chiefly 
valuable for its chemical compounds, particularly the various 
pigments, — chrome yellow and chrome green, and bichro- 
mate of potash, which is used in calico-printing. A small 
amount of the chromium supply is used in the manufac- 
ture of chrome steel, which is remarkable for its extreme 
hardness, and is used for burglar-proof safes, hard-edged 
tools, etc. 

The mineral is invariably chromite or chrome iron ore, a 
combination of ferric and chromic oxides in varying propor- 
tions, and often containing other substances as impurities. 
This mineral is one of the products of the alteration of min- 
erals and rocks to serpentine, and it occurs uniformly in 
association with serpentine. In America, chromite has been 
found in varying quantities throughout the belt of metamor- 
phic rocks from Maine southwards, wherever serpentine is 
found. Formerly mines were located in Maryland, and later 
in Pennsylvania, and, as a result of this, Baltimore became 
the centre of the chromium industry in this country, a posi- 
tion which it still holds in spite of the fact that the ores in 
this region are exhausted. At present the only important 
sources of chromite in the United States are in California, 
where it occurs in abundance. But, owing to the difficulties 
of transportation and the distance from the market, these 
deposits are exploited in a very indifferent manner, and 
there is very little profit in the attempt to compete in the 
eastern market with the Asiatic and European chromite. 



300 ECONOMIC GEOLOGY OF THE UNITED STATES. 

In the Urals, chrome iron ore is found in a number of 
places, and it is obtained also from Greece and Austria- 
Hungary ; but by far the most important source is in Asia 
Minor, near Brusa, fifty-seven miles east of Constantinople, 
where it occurs in pockets and bunches in serpentine. The 
greater part of our supply of this ore comes from there. 

In 1892 the chrome ore produced in this country amounted 
to about 3000 long tons, valued at $30,000, while the ore 
imported exceeded 5000 long tons, and the imports of chro- 
mate and bichromate of potash amounted to over 1,000,000 
pounds. We have abundant supplies of this ore, if we ever 
need to draw upon them, but the demand is limited and the 
foreign ores are much more favourably situated for exploita- 
tion and transportation. 

Iron Pyrite. 
Although an ore, this mineral is used as a source, not 
of the metal, but the non-metallic mineralizer, sulphur. 
This ore is sometimes a source of copper and also of gold, 
as has already been stated; but iron pyrite proper is of 
value only for its sulphur, and for this reason it is used 
in the manufacture of sulphuric acid. The marvellous 
increase in the demand for this acid, chiefly for the manu- 
facture of kerosene oil and superphosphates, calls for increas- 
ing supplies of pyrite. In 1870, 70,000 tons of sulphuric 
acid were manufactured in the United States; in 1880, 
285,000 tons; and in 1892, nearly 580,000 tons. At the 
same time the amount of iron pyrite mined has increased 
from 2000 long tons in 1880 to 106,250 tons in 1892. 
The imports of pyrite in 1892 amounted to 210,000 long 
tons. 



MISCELLANEOUS ORES. 301 

The iron pyrite mines of the United States are located 
chiefly in metamorphic rocks, slates and schists princi- 
pally, where the mineral occurs bedded, segregated, and 
in true veins. An extensive pyrite-bearing belt extends 
through Maryland, Virginia, and the Carolinas, but at 
present the principal source of the mineral in this belt is 
Virginia. Massachusetts has an output of 40,000 tons a 
year from the Davis mine in Franklin County. In the 
other New England states pyrite is common, but not much 
is produced. Indeed, surprisingly little attention has been 
paid in this country to this common but, when properly 
treated, often very valuable ore. Much of our supply of 
pyrite is foreign, coming chiefly from Canada, Newfound- 
land, and Spain. The occurrence there is not unlike that 
of the United States, and some of the ores are valuable 
also for their copper contents. The following table shows 
the pyrite production of some of the leading countries of 
the world : — 

PRODUCTION OF PYRITE IN THE WORLD, 1891. 

Metric Tons (2204 Lbs.). 

Spain 283,724! 

Germany 128,288 

United States 111,105 

Canada 59,312 

Hungary 50,000 2 

Italy 19,868 

Great Britain 15,716 3 

The output of pyrite from the United States in 1892 
(107,985 metric tons) was valued at 1357,000. 

1 Exported. 2 Estimated. 

3 In 1866 Great Britain produced 137,622 tons. 



302 ECONOMIC GEOLOGY OF THE UNITED STATES. 

G-eneral Review of Metals. 

Reviewing briefly, it may be said that silver and silver- 
bearing lead ores are found in a wide variety of associations, 
chiefly, however, in true veins, and in these, associated 
very commonly with other ores such as copper, zinc, tin, and 
gold. The ores of lead are numerous, but this metal is 
found almost invariably as the sulphide, or some mineral 
derived from the alteration of this. Aside from the argen- 
tiferous galena, lead is found abundantly in non-argentif- 
erous galena, in association with zinc blende, or some 
mineral derived from the alteration, of these; and in such 
association the mode of occurrence is almost uniformly in 
dolomitic limestone. Copper is also found in many diverse 
positions in the earth and in numerous mineral ogical asso- 
ciations ; but the two chief sources of the metal are native 
copper in one district and the sulphide in many districts. 
The latter ore frequently bears gold and silver, and it is 
not uncommon to find it associated with other ores as, for 
instance, in the famous English and German mines. One 
striking feature connected with copper ores is their almost 
universal association with igneous rocks, which appear to be 
their source, sometimes by the formation of contact accumu- 
lations, but more commonly by subsequent aggregation. 

Iron has numerous modes of occurrence, dependent upon 
a variety of circumstances, not the least important of which 
is the character of the ore itself. Brown hematite is typi- 
cally precipitated; red hematite is sometimes altered limo- 
nite, sometimes a replacement deposit. The carbonate is 
prevailingly concretionary in occurrence, and magnetite is 
frequently accumulated by segregation during metamor- 



MISCELLANEOUS ORES. 303 

phism. Nearly all of these deposits of iron are either 
bedded or have the appearance of being bedded, as the 
result of the peculiarity of their secondary accumulation 
by segregation or replacement. Manganese resembles iron 
in its mode of occurrence, particularly the brown hematite 
and carbonate, and the same is true of the ore of alumi- 
num, bauxite. Nickel and cobalt prevailingly occur in 
metamorphic rocks, chromium typically and almost uni- 
versally occurs in serpentine, and iron pyrite is also found 
in metamorphic rocks, chiefly iron-bearing slates and schists. 
Few metals have more typical modes of occurrence than 
gold, which occurs in superficial deposits derived from 
the disintegration of gold-bearing veins, themselves almost 
equally typical in the fact that they are quartz veins, 
bearing iron pyrite, and apparently usually of segregation 
origin. Gold ore is practically all native ; and in this 
there is a close resemblance to platinum, as there is also 
in the fact that both occur very commonly in stream 
gravels. This is the universal source of platinum, but this 
metal is also found in serpentine rocks, although since 
little is known concerning the source of platinum, this 
cannot be definitely stated to be the typical occurrence 
in the rock. Like gold and platinum, much of the tin 
that is mined comes from stream gravels, where it accu- 
mulates for the same reason that the other two metals 
do ; namely, its high specific gravity and practical inde- 
structibility. In the rock, tin is all but universally found 
in or near coarse granites, although some tin deposits 
occur in other igneous rocks. Finally, mercury is nearly 
always associated with igneous rocks of recent origin, and 
it is apparently a contact 'deposit, in part the result of 



304 ECONOMIC GEOLOGY OF THE UNITED STATES. 

sublimation. Both tin and mercury occur in typical ores, 
the first as an oxide, and the latter as a sulphide, and 
other occurrences may be considered rare. 

These generalizations must not be understood to be of uni- 
form application. There are exceptions to nearly all these 
statements ; but they are made as general remarks which 
have an application in the majority of cases. The examples 
on the preceding pages illustrate the principles here enun- 
ciated, and a more widespread study of ore deposits verifies 
them even more strikingly. Under the conditions above 
named, the various ores are usually found ; and consequently 
we may properly conclude that, under similar circumstances, 
other similar mineral deposits will generally be found; but 
while we may look to these modes of occurrence for the 
major part of our ore deposits, we need not be surprised to 
find wide variations from these types, and the reason for 
this is to be found in the widespread distribution of ore, in 
disseminated form, through the earth's crust, as well as the 
great variety of changes which the crust has undergone. 

The United States may be considered the great metal- 
producing country of the world. In the case of a very few 
metals, principally platinum and tin, we are practically non- 
producers, but in the others we hold a high rank. Our 
country stands first in the production of iron, gold, silver, 
and copper, the four most important metals ; second in the 
production of lead, zinc, and mercury, which are probably 
the next most important ; either third or fourth in the pro- 
duction of manganese and pyrite ; and it holds a minor rank 
in the production of nickel, cobalt, antimony, and chromium, 
which are distinctly minor metals. The following table 
shows the value of the metalliferous output of the country 



MISCELLANEOUS ORES. 305 

for 1892. The total metal production of the United States 
for 1892, exclusive of the ores mentioned in the table, was 
valued at $318,638,596, while in 1880 the value was only 
$201,283,094. 

PRODUCTION OF METALS AND METALLIC ORES IN THE 
UNITED STATES, 1892. 

Pig iron $136,806,915 

Silver 83,909,210 

Copper 37,850,000 

Gold 33,000,000 

Lead 17,917,000 

Zinc 7,703,580 

Mercury 1,119,720 

Pyrite 357,000 

Manganese ore 170,000 

Nickel 57,691 

Antimony 51,600 

Chrome-iron ore 30,000 

Tin . . 29,827 

Cobalt oxide 6,450 

Platinum 1,750 

The distribution of these products in the country is very 
marked. In only three states, Montana, Colorado, and Cali- 
fornia, are four of these metals found in sufficient abundance 
to give the state a rank among the first five ; and if 
chromium be excluded, California must be omitted. Montana 
is the most important state, Colorado second, Michigan third, 
and California fourth. The following table shows the dis- 
tribution of the metals, in the first five important states, 
when there are as many. It will be noticed that but 
eighteen states are included in such a table ; and if man- 
ganese is not included, the number is reduced to fifteen. If 



306 ECONOMIC GEOLOGY OF THE UNITED STATES. 

iron, manganese, and nickel are excluded, all of these states, 
with the exception of Michigan, Wisconsin, Missouri, and 
Kansas, are in the Cordilleras ; and the last two of these 
states are important only for lead and zinc. Thus the dis- 
tribution of these metals, in abundance, is extremely local. 
While nearly all of the metals are found in the states and 
territories of the far west, iron and manganese occur in 
the east, and zinc principally in the central states. There- 
fore, the fact that the United States is pre-eminently the 
country of metals is due chiefly to the peculiarities of the 
geology in the Cordilleras. 

In the following table the relative rank of the states, in 
the production of a given metal or ore, is indicated by 
numerals above the estimated value of the mineral product. 
For iron the value of the ore at the place of production* is 
given, instead of the value of the pig-iron production, which 
is much greater and differently distributed, this being not 
necessarily near the mines which produced the ore. The 
value of the iron production gives a different rank to the 
states from that which is given by amount of output, since 
different ores are of different values. This will be seen by 
comparison with the tables in the chapter on iron. The 
actual output of lead, zinc, and some of the minor metals is 
not well shown in the table; but this will suffice to illus- 
trate the general distribution, which is the object sought 
in the preparation of the table. 



MISCELLANEOUS ORES. 



307 



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Part III. 
NON-METALLIC MINERAL PRODUCTS. 



CHAPTER XIV. 

COAL. 

General Statement. — There is practically every gradation 
from peat to graphite. Many of the brown coals of Texas, 
and other parts of the west, contain woody fibres, only 
slightly altered from their original condition, and very 
closely resembling peat in many characteristics. These 
grade, sometimes in the same bed, to bituminous coal, which 
is soft and lustrous ; and this in turn may grade into semi- 
bituminous, a much harder, more compact, and purer coal. 
In New Mexico, where porphyry dikes have crossed a coal 
bed, bituminous coal is altered to anthracite ; and in Rhode 
Island, where coal beds have been subjected to marked 
regional metamorphism, graphite and graphitic anthracite 
have been produced. A final stage in the alteration would 
be the formation of a bed of graphite ; but we know of no 
such bed that can be directly traced to this origin, although 
some of the Rhode Island graphitic anthracites very closely 
approach this condition. 

Briefly, therefore, coal may be said to be altered vegetable 
accumulations, the degree of alteration producing different 
grades of coal, even up to anthracite. The alteration indi- 
cated by these changes consists partly in compacting the bed, 
but chiefly in driving off the volatile substances and water and 
concentrating the carbon. By this process, the percentage of 
carbon is increased, from as low as 5 per cent to 88 per cent, 

311 



312 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



and even more. The changes which result during this altera- 
tion are indicated in the following table of analyses : — 

ANALYSES OF PEAT, LIGNITE, AND COALS. 





Peat. 


Lignite. 


Bituminous Coal. 


Anthracite. 




Dismal 
Swamp. 


Athens, 
Texas. 


Atascosa 
County, 
Texas. 


Leon 
County, 
Texas. 


Waldrip, 
Texas. 


Penn- 

syl- 

vania. 


Penn- 

syl- 

vania. 


Penn- 
syl- 
vania. 


Penn- 
syl- 
vania. 


Moisture . . . 


78.89 


9.10 


13.285 


14.670 


4.55 


0.9 


1.3 


2.74 


2.93 


Volatile matter . 


13.84 


42.20 


■59.865 


37.320 


38.50 


25.63 


20.87 


4.25 


4.29 


Fixed carbon 


6.49 


7.37 


18.525 


41.070 


44.80 


51.30 


67.20 


81.51 


88.18 


Ash 


.78 


41.32 


8.325 


6.690 


12.14 


17.77 


8.80 


10.87 


4.04 


Sulphur . . . 




0.62 


2.360 


0.250 


7.96 


4.4 


1.83 


0.62 


0.55 



Coal is widely distributed throughout the world, and even 
in many countries where it is not mined it exists in great 
quantities. Europe and the United States produce practi- 
cally all the coal of the world ; and, in Europe, by far the 
greater part of the supply is found in Great Britain, Ger- 
many, France, Austria-Hungary, and Belgium. Our own 
country has a number of important areas. 1 Probably there 
are not far from 300,000 square miles of coal-bearing strata 
in this country ; but by no means is this all available coal, 
since over large areas it is either too thin or too impure 
for profitable extraction. The actual codl-producing area, 
either at present worked or available for the future, is not 
over 50,000 square miles, and of this only a small part is 
now being worked. 

1 Detailed descriptions of the coal areas of the United States will be 
found in the Eleventh Census volume on Mineral Industries, pp. 343-422, 
and in The Mineral Resources, Day (U. S. Geol. Survey), particularly the 
volume for 1891, pp. 177-402. 



• 



COAL. 313 

In the Eleventh Census report the coal-bearing strata of the 
country are divided into seven areas, as follows : (1) the 
New England basin, including a small section in Rhode Island 
and southern Massachusetts, having an area of about 500 
square miles ; (2) the Appalachian district, at present the 
most important, with an area of 65,000 square miles, and 
extending from Pennsylvania to Alabama ; (3) the Northern 
area, of about 7000 square miles, in Michigan ; (4) the Cen- 
tral area, 48,000 square miles in extent, embraced in the 
three states, Illinois, Indiana, and western Kentucky; 
(5) the Western area, a poorly defined region, covering more 
than 98,000 square miles, and divisible into many minor dis- 
tricts, extending more or less brokenly from Iowa to the Rio 
Grande ; (6) the Rocky Mountain area, of indefinite extent, 
with scattered basins known to exist in nearly all the states 
and territories of the Rocky Mountain belt; and (7) the 
Pacific Coast district, the area of which is also unknown, but 
in which are included the three states of Washington, Oregon, 
and California. An eighth area might well be added, to 
include the Alaskan coal fields, which will soon be developed. 

Coal, unlike the great majority of metalliferous deposits, is 
an actually bedded stratum, formed, as a part of the sediment- 
ary series, in a manner which is more fully referred to in the 
following pages. Before the development of our western 
country, coal, properly speaking, and excluding the lignites, 
was supposed to be the product of a single age, the Car- 
boniferous, and fuels of later origin were believed to be of 
very local nature and lignitic structure. But the opening of 
the coal mines in the Rocky Mountains has shown the fal- 
lacy of this belief, for here we find beds of all ages, since 
the Carboniferous, and in all stages of alteration, even to 



314 ECONOMIC GEOLOGY OF THE UNITED STATES. 

anthracite. The Cretaceous and Tertiary ages are, in this 
district, the most favoured with coal beds ; but this is doubt- 
less due, in large measure, to the fact that the rocks of these 
ages are much better developed than any of an age subsequent 
to the Carboniferous. With the exception of thin seams in 
the Lower Carboniferous and Devonian strata, there are no 
coal beds in rocks lower than the Coal Measures. 

New England Coal Basin. — This region is of interest, 
not for the amount produced, but for the peculiar nature of 
the coal. Although never a heavy producer, this region 
has been worked, more or less continuously, for a long 
period. Unlike the greater part of our coal, the beds of 
this district are highly tilted, and some of the mines have 
extended to a considerable depth. A few thousand tons 
are annually produced, but this burns with such difficulty 
that it is of use only where there is a strong draft, as in 
a blast furnace ; but this difficulty is partly compensated 
for by the length of time which it burns and the large 
amount of heat furnished. A very peculiar industry for 
a coal region has been recently begun upon the basis of 
the graphitic nature of these anthracites. This is the manu- 
facture of pipe-coverings, stove-facings, stove-blacking, and 
paints, which shows the peculiar condition of the coal beds. 

The graphitic nature of the anthracite is due to the 
metamorphism of the coal-bearing beds, by mountain-building 
forces, which have, by folding and faulting, resulted in 
altering the nature of the enclosing rocks, in some cases 
to well-defined schists. A considerable thickness resulting 
from folding is noticed in some of the beds of coal, that 
at Portsmouth being from three to ten feet thick ; and it 
is not impossible that, in some of the less metamorphosed 



COAL. 315 

parts of this area, valuable coal beds exist beneath the 
drift coating. This area may be considered a part of the 
coal-bearing series of Nova Scotia, the age being the same, 
and the conditions of formation similar, but the metamor- 
phism being much less in the latter district. 

Appalachian Coal District. — In this area are included 
the coal fields of Pennsylvania, Ohio, Maryland, Virginia, 
West Virginia, eastern Kentucky, Tennessee, Georgia, and 
Alabama ; and the Coal Measures are practically continuous 
from northern Pennsylvania to western Alabama. The coal 
beds follow the folds of the Appalachians and extend into 
the level plateau country at the western base of the moun- 
tains. While this coal is confined to a single age, the 
Upper Carboniferous, it is not a continuous layer, but a series 
of lenticular beds at different horizons in the Coal Meas- 
ures, varying in extent and in thickness, sometimes gradu- 
ally, sometimes abruptly, from a fraction of an inch to 
several feet. A thin seam may thus become thicker, in a 
given direction, and then again lose thickness ; and, in 
the shaft sunk to a coal bed, numerous seams of coal, of 
varying thickness, may be encountered. 

This coal was first discovered in Virginia in 1701, in Ohio 
in 1755, and in western Pennsylvania in 1759. The first coal 
mines regularly opened in the country were near Richmond, 
Virginia, in 1750. There are two kinds of coal in this district, 
the bituminous (including semi-bituminous) and the anthra- 
cite, both of which occur in the same series of rocks, the 
Coal Measures of the Carboniferous, but in different parts of 
the district. 

The anthracite fields, which produce practically all of 
this kind of coal in the country, are confined to the eastern 



316 ECONOMIC GEOLOGY OF THE UNITED STATES. 

part of Pennsylvania, where there are three general regions, 
the Wyoming, Lehigh, and Schuylkill, which are properly 
divisible into five well-defined fields or basins. Coal was 
first discovered here in 1790, and the first shipments were 
made in 1800 ; but not until 1825 was the region made to 
produce extensively, since the difficulty of burning the 
coal prevented consumers from attempting to use it. The 
reason for the occurrence of anthracite in this part of 
Pennsylvania, and its absence elsewhere in the district, 
is that the coal basins here have been subjected to a cer- 
tain amount of metamorphism by the folding which has 
produced the Appalachians. This folding is far less than 
that to which the Rhode Island-Massachusetts basin was 
subjected, but was sufficient to drive off much of the water 
and volatile matter and produce anthracite. It is probable 
that considerable quantities of this coal have been removed 
by the extensive denudation to which the Appalachians 
have been subjected since their formation. 

The following table is of interest, since it shows the 
increase in production of anthracite, in these fields, from 
the very first. Between 1820 and 1891 inclusive, the out- 
put of this region has amounted to 779,639,326 long tons, 
and the Wyoming district is the most important of the three. 

PRODUCTION OE ANTHRACITE IN PENNSYLVANIA. 
Long Tons (2240 Lbs.). 

1820 365 

1830 174,734 

1840 864,379 

1850 3,358,889 

1860 8,513,123 

1870 ... 16,182,191 

1880 23,437,242 

1890 36,615,459 

1891 • 40,448,336 



COAL. 317 

The bituminous field of the Appalachian area is far more 
important, in point of output, than any of the other regions ; 
and in this Pennsylvania is the greatest producer. This does 
not necessarily mean that there is a greater supply of coal 
here than elsewhere, but that there is a better market and 
consequently a greater development of the possibilities. The 
iron industry is largely responsible for this. Where coal is 
not found iron cannot be profitably mined, excepting under 
conditions of exceptional facilities for exploitation and trans- 
portation, which admit of the shipment of the ore to smelters 
near the coal supply. Both coal and iron occur in this belt ; 
and in development the two industries have progressed 
together, so that, at present, both iron smelting and coal 
mining are carried on, in this district, on a very extensive 
scale. So fixed is the industry of iron smelting here, that, 
even though the iron supply may decline, as it has and will 
continue to do, it will probably continue to increase and be 
fed with iron from outside, while the industry of coal mining 
will increase. There are other factors to be considered also, 
chiefly the fact that this region was the first to be developed 
industrially, and that it is favourably situated for transporta- 
tion of coal and articles manufactured by the aid of coal. 

In no state is the value of iron mining to coal production 
better shown than in Alabama, where, in 1870, the output of 
coal was only 13,000 short tons; in 1880, 380,000 tons; in 
1887, about 2,000,000 tons ; and in 1891, 4,759,781 tons. A 
comparison with the statistics of iron will show the relation of 
the two products. West Virginia has also had a remarkable 
increase, from 1,568,000 short tons in 1880, to 9,220,665 tons 
in 1891. Nearly all of the other states of the Appalachian 
district show a marked increase in coal output, and this 



318 ECONOMIC GEOLOGY OF THE UNITED STATES. 

is largely attributable to the increase in the output of iron 
manufactures. 

Central, Western, and Northern Coal Areas. — There is very 
little to be said about these areas. The Northern basin is of 
very slight importance, and in the past ten years it has 
decreased its output. Of the other two districts, the Central 
has a much larger output, and the states of both districts 
have steadily increased their production. The coal beds are 
in practically horizontal strata of the Coal Measures, and coal 
mining is, therefore, not usually difficult or expensive. Both 
the age and the conditions of accumulation, and, therefore, 
the modes of occurrence, are the same here as in the Appa- 
lachian district. 

It is doubtful if the division between the Western and 
Central areas is well founded, since the dividing line is the 
Mississippi, and the cause for the division is merely that this 
river has removed the Coal Measures from its valley. Mis- 
souri and Illinois belong to practically one geological area, 
and the division is highly artificial. It Avould be much bet- 
ter to have for the fifth division the Texas and other post- 
Carboniferous coals of the trans-Mississippi region. 

In the more western parts of the area, and in various por- 
tions of Texas, there are Cretaceous and Tertiary deposits of 
coal and lignite, some of which are mined for local purposes, 
but most of which are at present of no economic value. 
They form a reserve supply which can be drawn upon in 
the future; and some believe, in the very near future. The 
Texas field illustrates this occurrence, for, aside from a 
rather small and not very important area of true Carbonifer- 
ous coal, there are extensive deposits of both Cretaceous and 
Tertiary fuel in this state. On the Rio Grande, at several 



COAL. 319 

points, both lignite and bituminous coal, of Cretaceous age, 
occur; and, in eastern Texas, there are very thick beds of 
Tertiary lignite in the coastal deposits. These are easily 
mined, but, on account of their position, their impure nature, 
and friable structure, they do not seem to promise to be of 
immediate importance. 1 

Rocky Mountain, Pacific Coast, and Alaskan Coal Areas. — 
In these districts, coal, in the form of lignite, bituminous 
coal, and even anthracite, is found in several areas, and in 
strata of several geological ages, chiefly Tertiary and Creta- 
ceous, and more rarely Carboniferous. Some of these states 
have increased their output in the last decade at a remarka- 
ble rate, and this section may be considered the coal reserve of 
the country, for even the larger producers have by no means 
developed their coal fields to even one-half their capacity. 
The area and extent of these coal fields cannot be stated, 
but we know that there are immense supplies. Very little 
anthracite is found, and this is surprising when the changes 
through which these rocks have passed are considered. A 
bed of anthracite, about six feet thick, is found in Colorado, 
and another exists in New Mexico ; in both places the meta- 
morphism being that of contact with intrusive igneous rocks. 
This coal appears to be of as good quality as that of Pennsyl- 
vania. The bituminous coal of Colorado, although of Creta- 
ceous age, is also of excellent quality, and it occurs in thick 
and extensive beds. There is excellent prospect for the 
future of this state as a coal-producer, and the same is true 
of other states in this belt ; but the lack of market, and the 

1 These coals and the methods by which they may be utilized are described 
by E. T. Dumble in a Eeport on the Brown Coal and Lignite of Texas, pub- 
lished by the Texas Geological Survey. 



320 ECONOMIC GEOLOGY OF THE UNITED STATES. 

difficulty of convincing eastern people that this fuel is better 
than lignite, have interfered with the more rapid develop- 
ment of the fields. 

On the Pacific Coast the most important state as a coal- 
producer is Washington, where lignites, bituminous and 
anthracite coals are found, the different kinds being the 
result of different degrees of metamorphism caused locally by 
the intrusion of igneous rocks. With the development of the 
west these Cretaceous coals will be more and more valuable, 
and already the output has become important, having in- 
creased, since 1885, from 380,250 to 1,056,249 short tons. 

In Alaska, coal has long been known to exist, and there is 
promise of immediate development. The Russians knew of 
the existence of coal before they sold the territory to the 
United States, but the industrial and climatic conditions 
have interfered with its development. There are extensive 
and thick seams which can be easily worked. 

Of foreign deposits, nothing need be said, since no new fea- 
tures are illustrated. Coal is extremely widespread and abun- 
dant in all explored continents ; and, even with the present 
rapid production, there need be no fear of an exhaustion of the 
supply for many centuries to come. Not only are there great 
reserves in our western territory, but in the continents other 
than this and Europe, coal, though not produced in great 
quantities, is by no means scarce. It has been formed ever 
since the Carboniferous, whenever the conditions were favour- 
able, and this has been by no means an uncommon geologi- 
cal condition. There is good reason to believe that the 
demand will cease before the supply is exhausted. 

The following table shows the distribution of coal in the 
several areas of the country : — 



COAL. 



321 



PRODUCTION OF THE COAL AREAS OF THE UNITED STATES. 
Short Tons (2000 Lbs.). 



Akeas. 


1880. 


1887. 


1890. 


1891. 


Total 
1870-1892 

inclusive. 


f Bituminous, 
Appalachian < 

(. Anthracite, 

Central 

"Western 

Eocky ( Bituminous . 

Mountain \ Anthracite . 

Pacific Coast 

Northern 

New England Anthracite, 


29,834,622 

28,640,819 

8,150,195 

3,212,787 

1,067,314 

425,170 

100,800 

6,176 


55,193,034 

39,506,255 

14,478,883 

10,193,034 

3,646,280 

36,000 

854,308 

71,461 

6,000 


73,008,102 

46,468,641 

20,093,533 

10,470,439 

6,150,782 

55,0002 

1,435,914 

74,977 


77,984,563 
50,665,431 
20,327,323 
11,023,817 
7,185,707 

60,0002 
1,201,376 
80,073 
500 


933,909,305 
561,627,269! 
254,821,177 
138,470,000 
53,848,504 

12,313,040 
1,455,289 


Total 


71,437,883 


124,015,255 


157,788,656 


168,566,669 


1,956,444,584 



The total value of coal produced by the United States 
between 1870 and 1892 inclusive was 12,237,258,218. 

Origin of Coal. — That coal is derived from vegetation is 
proved by a number of indisputable facts. In the first place, 
its carbonaceous nature is strongly suggestive of this origin, 
and, in the less altered coals, the vegetable origin is proved 
by the actual presence of plant fibres, seeds, etc. Even 
where, with the naked eye, stems of plants and impressions 
of ferns cannot be seen, unless the coal is too greatly meta- 
morphosed a microscopic study shows the presence of woody 
fibre and plant remains of one kind and another. Indeed, 
actual tree trunks are quite perfectly preserved, and, in 
some cases, although the strata have been tilted and dis- 
turbed, these trees rise through the coal beds, at right angles 
to the stratification, with their roots extending into the clay 

1 Includes Rocky Mountain anthracite. 2 Estimated. 



322 ECONOMIC GEOLOGY OF THE UNITED STATES. 

beneath the coal. Such a condition has been observed in 
the Nova Scotia coal fields and elsewhere. The tree trunks 
stand where they grew, just as some trunks of trees stand 
at present in bogs, either partly or completely buried. 

These facts prove the point that vegetation is the origin 
of coal, but in just what manner these accumulations were 
made is not quite so clear. The accumulation of peat bogs is 
familiar to all who have dwelt in northern lands. A pond is 
partly filled with sediment, it then becomes transformed to a 
morass, and eventually to a swamp, by the growth and decay 
of vegetation, first reeds, then moss, and finally bushes and 
trees. Year after year additions are made to the vegetable 
accumulations, until, finally, a bed of peat is formed ; and in 
the typical peat bed, one of the most important of the bog- 
forming plants is a moss belonging to the genus Sphagnum. 
This vegetation, dying upon the surface, would not accumu- 
late, for, as is well known, organic remains quickly decay in 
the air ; but beneath water this destruction is arrested and the 
vegetation even preserved by the various organic acids pro- 
duced by a partial decay. Thus, it is not uncommon to find 
tree trunks in swamps, at a depth of several feet beneath the 
surface, so perfectly preserved that the marks of beaver teeth 
can be seen, although these were made perhaps several cen- 
turies or even a thousand years ago, when the swamp was 
inhabited by beaver. 

One might at first assume that, since there is every grada- 
tion between peat and coal, the original condition of coal was 
actually peat, and this has given rise to the Peat Bog Theory 1 
for the origin of coal. This may have been the origin of 

1 On the Vegetable Origin of Coal, Lesquereux, Annual Report, Pennsyl- 
vania Geological Survey, 1885, pp. 95-124. 



coal. 323 

some coal beds, particularly those of the western Tertiary 
strata, which were deposited in inland seas and lakes. With 
many of the Carboniferous coal beds, and also some of those 
more recently formed, another mode of origin must be 
sought. By a study of the coal beds it is found, that, both 
beneath and above, there are clays, limestones, and sandstones 
of marine origin and containing marine fossils. The coal is 
therefore directly associated, in point of origin, with the sea. 
Indeed, there are rapid and striking alternations from coal 
to sedimentary beds, then to coal, and so on, often for scores 
of feet vertically. Sometimes the coal beds are thin seams, 
mere films of carbonaceous matter, but at other times they 
assume a thickness of a number of feet. Although both 
overlain and underlain by marine sediments, the coal plants 
themselves are not marine, but of types which, so far as 
we know, are at present exclusively dwellers on the land. 
Therefore we must find an explanation which will account 
for the accumulation of land plants either in or very close to 
the sea. Moreover, conditions for the preservation of the 
plant tissue must be present, and these conditions are evi- 
dently the presence of bodies of water, either salt or fresh. 

Two possible explanations suggest themselves: one, that 
the coal plants have been Avashecl into the sea; the other, that 
they grew on or near the shore line and fell into shallow 
bodies of water. The first of these, which may be called the 
Estuary Theory, is that rivers carried vegetation down with 
them, and caused it to accumulate in estuaries and bays at 
the mouths of the rivers. There seems to be very little 
reason to doubt that this, like the peat bog theory just de- 
scribed, is an actual cause for some such deposits. In the 
delta of the Mississippi, vegetable accumulations are en- 



324 ECONOMIC GEOLOGY OF THE UNITED STATES. 

countered in borings, and these are the result of the strand- 
ing and accumulation of rafts of timber which have been 
floating down the river for centuries. Even at present, al- 
though much of the forest of the valley has been removed, 
portions of the bank are undermined during the floods of the 
river, and the trees and bushes which grew upon them are 
floated off toward the sea. But, while this may be admitted 
as a possible, indeed as an actual cause, it cannot be extended 
to include all or even a large number of the coal beds. 
There are numerous fatal objections to the universal appli- 
cation of this theory. In the first place, a river transport- 
ing logs carries sediment also, and beds so formed will be 
much more impure than coal beds usually are ; secondly, 
such deposits must be local and of a more limited area than 
many of our coal basins ; thirdly, under such conditions the 
plant fragments must be water-worn and broken, and we 
could hardly expect to have preserved in abundance, as we 
really do, even the most delicate parts of very fragile ferns ; 
and, finally, it is not probable that in such deposits tree 
trunks would grow and be preserved in place as they are in 
some coal strata. 

In support of this theory it may be urged that the coal 
occurs in basins, or linear areas, which might well be estu- 
aries ; but this is also exactly what is demanded by the third 
theory, which may be called the Seaeoast Swamp Theory. 
Aside from the objections urged above, against the estuary 
theory, none of which apply to this one, it is a notable fact 
that beneath coal beds there is commonly a clay stratum, 
called fire clay, which owes its peculiar properties to the 
absence of certain soluble salts needed by vegetation ; and 
this suggests strongly that the soils have been robbed of 



coal. 325 

these elements by plants, and most probably by the plants 
that have been accumulated in the overlying coal beds. If 
we assume the existence, during the coal period, of coastal 
swamps and lagoons, such as exist at present on many coasts, 
and are well illustrated by the marshes about Newark and Jer- 
sey City in New Jersey, all of the facts connected with most 
coal beds are easily explained. There are in the coal basins 
even channels similar to salt marsh channels or coastal rivers. 

It is also a fair assumption to make, that much of the coal- 
forming vegetation could grow in such places. At present, 
only a very few plants can live in salt water, or in places 
invaded by salt water; but, if one thing has been more 
plainly taught by geology than any other, it is that animals 
and plants have changed, not only in form and development, 
but in habits ; and, since it is not improbable that land vege- 
tation came originally from oceanic types, the change in habit 
here suggested is certainly possible, and we may even say, 
probable. On the eastern coast of the United States there 
are a number of phenserogams living, not only on salt 
marshes, but one, the eel grass, growing and flowering en- 
tirely submerged in salt water; and, on the Florida coast, 
the mangrove tree grows with its roots in salt water. No 
especial incredulity need, therefore, be felt in considering the 
possibility of a more widespread adoption of this habit by 
the Carboniferous vegetation, which differed so markedly 
from the present types of plant life. It is not, however, abso- 
lutely necessary to assume this condition, for it is possible 
that there existed along the shore line extensive swamps 
which were either fresh or only slightly saline. 

A study of coal deposits indicates not a single, but several 
explanations for their origin. Some were formed as peat 



326 ECONOMIC GEOLOGY OE THE UNITED STATES. 

bogs ; some, particularly those of the western Tertiary and 
Cretaceous areas, were formed upon the margins of lakes and 
inland seas ; not a few were, no doubt, accumulated in sea- 
shore estuaries ; and probably most of the Carboniferous coal 
beds were formed along coast lines in shallow lagoons, or 
seacoast swamps, either fresh or saline, and probably both. 
Attention may be called, in this connection, to the fact that 
the geological conditions in this country favoured the latter 
mode of accumulation in the three important coal-bearing 
ages. During the close of the Carboniferous period a great 
sea was beginning to be transformed to land, as the fore- 
shadowing of the development of the Appalachian Mountains 
and the central plateau. Skirting the old, pre-Palasozoic 
mountain area of the seacoast states, there stretched west- 
ward a region of shallow water and low, swampy land, upon 
which the coal vegetation grew. In the Central area, and 
in parts of the Cordilleras, the same conditions prevailed; 
but, in the latter region, these were better developed in 
Cretaceous and Tertiary times ; and here, by the mountain 
growth, large inland seas and lakes were produced, in which 
coal beds were accumulated. 

Conditions existing in Carboniferous Times. — A number of 
interesting questions arise concerning the conditions exist- 
ing in the Carboniferous period. Why do we find such rapid 
alternations of coal beds with marine sediments? It has 
been held that this is due to rapid alternations in sea-level, 
or, rather, land position ; that the land rose and fell, now 
being occupied by swamp plants, again submerged by the 
ocean, and this followed by other similar alternations of level 
and condition. This may be true; but so many alternations 
are called for, none of them producing high land, that some 



coal. 327 

simpler explanation may be sought. These phenomena may 
be accounted for by assuming a swampy land area, not un- 
like the coastal plains of Texas, gradually sinking, but with 
occasional halts, or periods of less rapid sinking. When 
land existed, plants grew ; but, if the submergence were more 
rapid than the building up, water prevailed until the 
rate of sinking was less rapid than the rate of filling. 
When such a period of slow submergence, or perhaps 
even absence of submergence, prevailed, sediment filled 
the bays, vegetation grew upon their margins, lagoons were 
built behind bars, and salt marshes were formed, just as 
they are at present, under the same conditions. In this 
manner the apparent elevations may have resulted from fill- 
ing rather than actual rising of the land. So, by a gradual 
submergence, a mere variation in rate will bring about all 
the conditions of alternation ordinarily noticed in coal 
beds. This does not deny the possibility of elevations also, 
for these would cause the alternations even more rapidly; 
but it does call in question the necessity of a theory which 
requires a large number and great variety of elevations and 
submergences, since this necessitates an instability of the land 
rarely witnessed anywhere outside of local volcanic areas, 
and our immense coal fields were not formed in such places. 

Another question that may be asked is, what were the 
climatic conditions in the Carboniferous period? It has. 
been very commonly assumed that the climate was moist, 
tropical in heat, and the atmosphere laden with carbonic 
acid gas for plant food. The large size, and apparent lux- 
uriance of the vegetation, resembling our present tropical 
flora, have been appealed to in support of this. That the 
climatic conditions were different from the present, even as 



328 ECONOMIC GEOLOGY OF THE UNITED STATES. 

late as the Tertiary period, is proved by a study of the 
Arctic regions, where not only animal and plant fossils, 
but even coal beds, are found in the rocks now situated 
in a region of perpetual snow. The value of the evidence 
in favour of these, from our present standpoint, abnormal 
conditions, has, it seems to the author, been unduly mag- 
nified. The evidence of luxuriant Carboniferous vegetation 
does not appear of so much importance when one has seen 
the giant trees of California and the primaeval forests of 
Canada. A good soil and a moist, and not too cold climate, 
will produce striking results in vegetation. It is doubtful 
if any trees in the Carboniferous period exceeded in size 
the giant Sequoia of California. Moreover, fossils of animals 
show us plainly enough that types which are now small 
throughout the world were once gigantic in size ; and the 
same may be equally true of plants. A new field and a 
newly acquired habit give to both animals and plants great 
powers of remarkable development. Before the Carbonif- 
erous period practically no land plants existed, and the soil 
was not, therefore, robbed of its plant food. Moreover, the 
Carboniferous land was made of a virgin soil just elevated 
above sea-level. Under such conditions, with a temperate 
climate, a luxuriant vegetation might easily be developed. 
It seems that we must grant moistness to the atmosphere, 
and the presence of oceans, where now is land, transforming 
the old mountain areas of the east into islands, makes such 
an assumption entirely within reason. When one reads the 
accounts of Russell 1 describing the luxuriant, almost trop- 

1 An expedition to Mount St. Elias, Alaska, National Geographic Maga- 
zine, III, 1891, pp. 53-204 ; American Journal of Science, XLIII, 1892. 
p. 178 ; Journal of Geology, I, 1893, p. 233. 



coal. 329 

ically luxuriant, forest at present actually growing on a 
moraine which rests on a living body of ice, near the 
terminus of the great Malaspina glacier of Alaska, he is 
ready to believe that no great revolution of climate is 
necessary to carry the vegetation of the Carboniferous 
period as far within the Arctic circle as man himself has 
penetrated. Transform the highlands of the Arctic to low- 
lands, and much of the ice will disappear ; then add to this 
a slight increase in the mean annual temperature, and vege- 
tation would find a home there. Peary, Lock wood, and 
others, state that the land lying north of Greenland is free 
from snow in summer, notwithstanding the presence of the 
great Greenland glacier to the south and of a frozen ocean 
all about. This is due in large measure to the fact that the 
land is low ; and if the mountains and highlands of Green- 
land were lowered to near sea-level, the climatic conditions of 
the Arctic would be greatly changed. Climate is strikingly 
dependent upon geography. 

The object in presenting these considerations is not to 
deny the possibility, nor even to question the probability, 
of a marked change in climatic conditions in the northern 
hemisphere during Carboniferous times, but to point out 
the fallacy of the statement so frequently made, that trop- 
ical conditions extended to the poles. Possibly this was the 
case, but probably it was not, and, in any event, the argu- 
ment upon which these statements are chiefly based, the 
resemblance of the coal flora to our present tropical flora, 
is not of much value after the lapse of time and the striking 
changes which have taken place in form and habit of fauna 
and flora since the Carboniferous period. 

The question is sometimes asked, why are coal beds not 



330 ECONOMIC GEOLOGY OF THE UNITED STATES. 

present in periods earlier than the Carboniferous? and the 
answer is, simply, that land vegetation had not been evolved 
in great luxuriance in earlier periods. A current statement, 
frequently found in text-books, is, that the reason for this 
was ' the too great abundance of carbonic acid gas in the 
atmosphere. According to this assumption, the early land 
vegetation laboriously extracted this carbonic dioxide, until 
just the proper percentage remained for the luxuriant Car- 
boniferous vegetation, but too much for air-breathing ani- 
mals, which came after the atmosphere had been cleared 
of the deleterious gas by the Carboniferous plants, — having 
the way prepared for them, as it were. Aside from the 
logic of animal and plant succession, which is as above 
stated, and which is readily explained in another way, — 
namely, normal evolution, — it is difficult to see upon what 
basis this assumption of an excess of carbonic acid gas in 
the atmosphere is based. To be sure, carbon taken from 
the air is sealed in the rocks in the form of both animal 
and plant remains ; but, on the other hand, it is being 
liberated by the decay of rocks ; and it is very doubtful 
if the supply of this gas in the atmosphere is sensibly 
different to-day from what it was in the beginning of the 
Carboniferous. 

If we should grant the assumption, for the sake of argu- 
ment, it would seem that a gradual decrease in amount 
and luxuriance of vegetation would necessarily follow upon 
the exhaustion of the carbonic dioxide ; but, on the con- 
trary, vegetation has increased in height of development 
and has certainly not lost in luxuriance. Ever since the 
Carboniferous the land areas of all the world have been 
clothed with vegetation, and so they are to-day. Moreover, 



COAL. 331 

if geological interpretations have been correctly made, there 
is more land at present than ever before, and this land 
has been continuously increasing in amount since the Car- 
boniferous. The simple fact is, that the greater part of the 
carbon taken from the air is given back again when the plant 
or animal dies, and the place of that stored away in the 
rocks is fully filled by supplies furnished by rock decay. 

Uses of Coal. — It would be difficult to make a compari- 
son between the value of coal and iron, since both are so 
important and intimately related. Probably, however, 
iron must be considered of more value, since there are 
so many possible uses for it, and no available substitute, 
whereas coal is not an actual necessity, although in the 
present state of industry it seems to be. The importance 
of the coal industry is shown by the fact that in 1892 
coal valued at not far from 1200,000,000 at the mines was 
produced in this country, and in 1891, 205,000 persons were 
employed, directly or indirectly, in the production of coal. 
Of bituminous and anthracite coal, the country produced 
171,769,355 short tons in 1892, 49,735,744 tons of this 
being anthracite, and the balance bituminous (including 
all varieties of coal excepting anthracite). Our exports 
in 1892 amounted to nearly 2,500,000 tons, and our 
imports to a little over 1,000,000 tons. The consumption 
of coal in the country per capita amounted to 5234 
pounds. 

Undoubtedly the most important single use of coal is 
as fuel for heating and cooking purposes; but as fuel in 
the manufacture of materials requiring heat, immense quan- 
tities are called for as well as in the production of energy 
in the form of steam. Our locomotives and engines for 



332 ECONOMIC GEOLOGY OF THE UNITED STATES. 

manufactories and for steamships are consuming coal at 
a remarkable rate which is every day increasing; and the 
rapid expansion of electric transportation in small towns 
and suburban districts is also increasing the demand for this 
fuel. One of the most remarkable advances in the use of 
coal is that made in the manufacture of pig iron and steel. 
Bituminous coal, transformed to coke by driving off the 
volatile substances in ovens, is rapidly supplanting anthra- 
cite and charcoal. Whereas in 1880 only 5,237,741 short 
tons of coal were used for this purpose, in 1891, 16,344,540 
tons were consumed, producing 10,352,688 tons of coke 
valued at 120,393,216. A relative decrease must have been 
caused in the consumption of coal for coal gas by the 
introduction of electric lights ; but the falling of! in this 
respect is more than compensated for by the increased 
demand for coal in the production of electricity. 

It is an interesting question what the future of coal will 
be. Some predict that the supply will fail us, and these 
favour more economical methods of production and use ; 
but, while this may be true of localities, and even of some 
countries, there seems to be no need to fear it in this 
country, nor in the world, for such a length of time that 
we need hardly trouble ourselves with the question. The 
tendency of the present seems to be rather toward a decrease 
in demand than a decrease in supply. This has not as yet 
made itself distinctly apparent, nor is it an absolute cer- 
tainty; but when we learn to economically win our elec- 
tricity from the wasted forces of nature, the waterfalls, or, 
as some predict, from heat direct, and then learn to store 
it for transportation, and to convert it from electrical 
energy to heat energy, there will come a time when coal 



COAL. 



333 



will be found of much less value than at present. This 
is now little more than a dream, but wonderful things 
are being done with electricity, and electricians assure us 
that we have hardly begun. 

Production of Coal. — In the production of the metallic 
minerals the far west was found to be of prime importance, 
but in the non-metallic products of the earth that section 
of the country assumes a much lower rank. The reason 
for this is that already given for the absence of an impor- 
tant iron output in the west, — less a lack of supply than 
an absence of market, or, in other words, a smaller degree 
of industrial progress. The following tables of coal output 
illustrate this distribution and other features connected 
with the production of coal at home and abroad : — 

PKODUCTION OF COAL IN THE UNITED STATES. 
Short Tons (2000 Lbs.). 



States. 


1870. 


1875. 


1880. 


1885. 


1890. 


1892. 


Pennsylvania ) 
(Anthracite) ) 


15,650,275 


23,120,730 


26,249,711 


38,335,973 


46,468,640 


49,735,744 


Pennsylvania ) 
(Bituminous) j 


7,T98,51T 


11,760,000 


21,280,000 


26,000,000 


42,302,173 


41,424,984 


Illinois . . . 


2,624,163 


3,920,000 


4,480,000 


11,834,459 


15,274,727 


17,949,989 


Ohio .... 


2,527,284 


5,447,970 


7,840,000 


8,754,120 


13,203,522 


14,560,000 


West Virginia . 


618,878 


1,120,000 


1,404,008 


3,369,061 


6,002,800 


8,710,878 


Alabama . . 


10,999 


67,200 


380,000 


2,492,000 


4,090,409 


5,275,000 


Maryland . . 


1,819,824 


2,623,905 


2,692,497 


2,833,337 


3,357,813 


4,036,283 


Iowa .... 


263,4S7 


1,120,000 


1,792,000 


4,012,575 


4,021,739 


3,820,000 


Colorado . . 


4,500 


98,838 


375,000 


1,398,796 


3,075,781 


3,771,234 


Indiana . . . 


437,870 


896,000 


1,680,000 


2,375,000 


3,305,737 


3,309,700 


Kentucky . . 


150,582 


560,000 


1,120,000 


1,904,000 


2,483,144 


3,020,050 


Missouri . . 


621,930 


840,000 


1,680,000 


3,080,000 


2,437,399 


3,017,285 


Total for the ) 
United States, f 


33,003,315 


53,121,029 


73,647,997 


112,609,811 


156,073,611 


171,769,355 



334 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Besides these states, four others, Kansas, Tennessee, Indian 
Territory, and Washington, produce between 1,000,000 and 
3,000,000 tons annually, and the first two more than 2,000,000 
tons. A noteworthy feature of this table is the rapid in- 
crease in the coal output of all the states, but especially 
of Alabama and Colorado. It is also a striking fact that 
the three leading coal-producing states in 1870 maintained 
their position in 1892. These three states, Pennsylvania, 
Illinois, and Ohio, together produced, in 1892, 123,670,000 
tons out of the total 171,769,000 tons produced by the 
country. Pennsylvania supplied considerably more than 
one-half the total of the United States, but the percent- 
age of Pennsylvania's output to that of the rest of the 
country has decreased considerably since 1870, owing to 
the rapid increase in output in other parts of the country. 
In twenty-three years the United States has increased its 
coal output to more than five times the amount at the 
beginning of that period, or at the average rate of more 
than 6,000,000 tons a year. 

The average cost of bituminous coal at the mines in 
Pennsylvania in 1891 was |1.00 a ton, and of anthracite 
coal 81.79 a ton. Therefore the value of the total output 
of 168,566,669 short tons was 8191,133,135. This of course 
does not at all represent the retail price, after shipping 
and passing through the hands of dealers, for this price 
varies greatly according to a variety of conditions, chiefly 
the distance from the mine and the manipulations of coal 
combinations. 



COAL. 



335 



PRODUCTION OF COAL IN THE WORLD.i 
Metric Tons (2204 Lbs.). 



Countries 


1865. 


1870. 


1875. 


1880. 


1885. 


1891. 


Great Britain 


99,759,613 


112,241,531 


135,491,837 


149,378,744 


161,963,736 


188,519,767 


United States 


24,790,400 


29,948,562 


48,204,201 


66,831,213 


102,186,761 


153,851,132 


Germany . 


28,327,800 


34,880,600 


48,532,400 


59,118,035 


73,675,515 


94,252,278 


Austria -Hun 
gary . . 


[ 2,028,089 


8,355,945 


13,062,738 


14,800,000 


20,435,463 


27,000,000 


France . . 


11,840,000 


13,300,000 


16,956,840 


19,361,564 


19,510,530 


26,199,745 


Belgium . 


11,840,603 


13,697,110 


15,011,331 


16,886,698 


17,437,603 


19,865,345 


Eussia . . 


331,000 


696,209 


1,171,736 


3,266,844 


4,273,476 


7,000,000 2 


Spain . . 


450,000 


661,932 


610,000 


847,128 


945,904 


1,286,000 


All Other 
Countries 


[ 2,712,495 


4,041,111 


6,25S,917 


9,079,774 


12,389,072 


17,126,733 


Total fo 
World 


r | 182,080,000 


217,823,000 


285,300,000 


339,370,000 


412,818,000 


535,101,000 



The rapid increase in output of nearly all the countries is a 
striking feature of this table ; but this is particularly notice- 
able in the case of the United States, Austria-Hungary, and 
Russia, and the group of unspecified countries. Spain, France, 
and Belgium have shown a smaller rate of increase ; and the 
two latter countries have fallen in rank, although they have 
increased their output. The marvellous increase in the 
coal production of the United States is especially note- 
worthy ; and it will not be surprising if, in the next decade, 

1 This extremely valuable table is extracted from a more complete one 
in Rothwell's Mineral Industry (p. 84), which has served as the source of 
many of our statistics. Any student interested in the statistics of mineral 
production will find this subject admirably and fully presented in that 
treatise. 

2 Probably the output of Russia for 1891 was nearer 8,000,000. 



336 ECONOMIC GEOLOGY OF THE UNITED STATES. 

this country assumes first place among the coal-producing 
nations, which it can easily do, if the demand increases suffi- 
ciently, since our possibilities are certainly exceeded by no 
other country in the world. Over three-fifths of the coal of 
the world is obtained in the United States and Great Britain. 
In the last twenty-seven years the average rate of increase 
in the coal output of the world has been about 13,000,000 
tons a year. 






CHAPTER XV. 

PETROLEUM, NATURAL GAS, AND ASPHALTUM. 1 

Petroleum. 

General Statement. — Petroleum, natural gas, and salt water 
frequently occur, more or less intimately associated, in strati- 
fied rocks. While sandstones and conglomerates are the 
chief sources of these substances, they are by no means 
confined to these rocks; but in some places are found in 
shales, in others, in limestones. The geological age of the 
petroleum-bearing strata is also variable. In the eastern 
states this substance occurs chiefly in the Silurian and Devo- 
nian sandstones and conglomerates, but some is also found 
in the Carboniferous strata. Practically no oil occurs in 
strata earlier than the Silurian. By far the most important 
single source of oil, at present, is the Trenton limestone 
horizon of the Silurian, in which the Ohio and Indiana fields 
are situated. Shales of the Laramie stage of the Cretaceous 
bear oil in Colorado ; and in California the age of the oil- 

1 The statistics and distribution of these substances in the United States 
are fully treated in the Eleventh Census volume on Mineral Industries, pp. 
425-591; in Roth well's Mineral Industry; and the various volumes of The 
Mineral Besources of the United States, Day (U. S. Geol. Survey). The 
geology of the subject is discussed by Orton in the Eighth Ann. Rept. U. S. 
Geol. Survey, 1889, pp. 475-662. There is also an important discussion of 
the subject in the Tenth Census, Vol. X., pp. 1-319. Various reports of the 
State Surveys of Ohio and Pennsylvania also contain discussions on petro- 
leum. A complete bibliography of the subject will be found in Carll's re- 
port, Annual Report for 1886, Part II., pp. 830-895. 

337 



338 ECONOMIC GEOLOGY OF THE UNITED STATES. 

bearing strata is Tertiary. Thus, although in the early his- 
tory of the petroleum industry the Palaeozoic was believed 
to be the only source of oil, it is now found to range through 
all ages from Lower Silurian to Tertiary. 

From the very earliest times in the history of this country, 
the existence of petroleum has been known, by reason of its 
seepage at the surface, in oil springs; but before the dis- 
covery of oil in a well at Titusville, Pennsylvania, in 1859, 
no petroleum was produced. Immediately after this discov- 
ery, explorations were begun elsewhere in Pennsylvania ; and 
these have been extended, practically all over the country, 
with the result of finding oil in the majority of the states, 
although the profitable production is confined to a few dis- 
tricts. Many remarkable developments have been made, par- 
ticularly those in 1885, when the importance of the Trenton 
limestone was first recognized. There are undoubtedly 
other fields yet to be discovered ; for even in as thoroughly 
explored a state as Pennsylvania, new fields of great impor- 
tance were discovered only a few years ago. 

Distribution of Petroleum. — Petroleum occurs, in rather lim- 
ited areas, in various parts of the United States. The well- 
known oil regions, which produce the greater part of the 
supply of the country, are the western Pennsylvania-New 
York field, two fields in Ohio, the West Virginia field, one 
in Colorado, and one in California. Although a few other 
states produce some oil, none of these are of immediate 
promise; but the past history of the petroleum industry is 
such that it is not safe to make predictions with reference 
to the possible future of these districts. Outside of the 
United States, the principal oil fields are in the Caspian 
region, Canada, Japan, and New Zealand; but the United 



PETROLEUM, NATURAL GAS, AND ASPHALTUM. 339 

States and Russia are far more important than all the 
others. 

Little need be said with reference to the distribution of 
petroleum, aside from the above general remarks and the 
statistics in the latter part of this section. Until 1875 all 
the petroleum of the country came from the Pennsylvania- 
New York field, which is continuous, and must therefore be 
considered as one field. Various oil-bearing sands of Devo- 
nian age are found there, in irregular areas, and since 1859 
they have been productive. Even as late as 1891, important 
developments were made, in this district, by the discovery 
of an oil pool called the McDonald field, which, in the latter 
part of 1891, had a production of 84,000 barrels a day ; but 
this has decreased, and at the close of 1892 the daily flow 
was about 18,000 barrels. In the last six months of 1891, 
it is estimated that 6,000,000 barrels of petroleum were pro- 
duced from this field. Most of the old wells have dimin- 
ished their flow, and many of them are now non-productive. 
New supplies will probably continue to be found in this field 
at intervals ; but eventually this will cease to be the case, and 
the old ones will probably give out. This seems to be the 
future of the petroleum industry, and already there are signs 
of its approach. 

During 1892, West Virginia increased its output by sup- 
plies from newly discovered fields in the same general belt 
as that of Pennsylvania. Since 1885, Ohio has assumed 
marked importance in this industry by the discovery of 
oil in large pools in various parts of the Trenton limestone. 
In Colorado there is a small area, called the Florence field, 
which has produced, and still continues to produce, consid- 
erable oil from a bituminous shale in the upper strata of the 



340 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Cretaceous. The California oil comes from sands bedded 
with shales of Tertiary age. . These oils are quite remarkable 
from the fact that they occur in highly tilted strata, instead 
of in nearly horizontal rocks, as is usually the case. In 
Russia, oil occurs in the region of the Caspian, in Canada in 
the province of Quebec, and oil is also found in Japan, in 
Peru, New Zealand, and in small quantities in several Euro- 
pean countries. 

Origin of Petroleum. 1 — - There are great variations in the 
character of petroleum, not only in different districts, but 
even in the same field. Some are dark and heavy, others 
are comparatively light and clear, the former being better 
lubricating oils, the latter serving as a basis for the produc- 
tion of illuminating oils. In some, the solid basis is paraf- 
fin, but those of California have asphaltum for a basis. There 
is a resemblance between natural oils and certain oils pro- 
duced from the distillation of animal remains such as men- 
haden oil, and between natural gas and gases produced 
artificially from coal, and from the decay of organic remains. 
Indeed, natural gas is principally composed of marsh gas. 
This has led to the theory that these substances are- the 
result of natural distillation of organic remains, in the 
rocks, and this theory is quite generally accepted by Amer- 
ican students of the subject. It may be stated that theories 
have been offered to account for petroleum and natural 
gas by chemical reactions between inorganic substances; 
but, although offered by eminent chemists, the theory has 
little to recommend it aside from the fact that changes 
such as are suggested would produce petroleum. The 

1 This subject is discussed by J. F. Carll in Keport III., Pennsylvania 
Geol. Survey, pp. 270-284. 



PETROLEUM, NATURAL GAS, AND ASPHALTUM. 341 

geology of the oil fields excludes these theories. By the 
decay of vegetation hydrocarbons of gaseous, liquid, and 
solid nature result, and by a concentration of the solid and 
liquid products, through the loss of the gaseous hydrocar- 
bons, petroleum is produced, and by a still further process of 
concentration solid paraffins or asphalts are formed. A 
chemical analysis of natural oils and gases would show 
a close resemblance to those artificially produced, but the 
chemistry of the hydrocarbons is so complex that little can 
be given in this connection. Naphtha, benzine, illuminating 
oils, etc., compose it. 

While we must believe that these substances are derived 
from the decomposition of organic matter, there is an oppor- 
tunity for a variety of explanations of the process by which 
this was brought about. Some have held that vegetable 
matter has produced the hydrocarbons, and others, that the 
source is from animal fossils ; probably each and a combina- 
tion of the two are correct for different fields. A study of 
the stratified rocks shows that certain shales and limestones 
are highly bituminous and that some are foetid from the 
odour of decayed animal remains. There are abundant rea- 
sons for the belief that petroleum has resulted from the slow 
destruction of organic remains, both animal and vegetable, 
during the changes through which the rocks have passed. 

It has been suggested that the source of the hydrocarbons 
is the coal, these having been driven off, with comparative 
rapidity, by a process of destructive distillation analogous to 
the production of artificial oils and gases. Unfortunately 
for this theory the greatest supply of these substances comes 
from rocks below the horizon of the coal, and moreover the 
larger oil fields are in horizontal rocks which have undergone 



342 ECONOMIC GEOLOGY OF THE UNITED STATES. 

very little metamorphism. Therefore, while it must be ad- 
mitted that this is a possible source, it is not the source of 
the bulk of our petroleum. Destructive distillation may 
account for the oil in the tilted rocks of California, and for 
the Colorado oils, but it cannot be accepted for the fields of 
the east. 

The distribution of oil and gas through the rocks presents 
many interesting features. At first they were supposed to 
be confined to the rocks beneath the valleys, the theory of 
the well-drillers being, that in some way the surface topog- 
raphy influenced the distribution of the petroleum; but there 
is of course no such association. A thorough study of the oil 
fields thus far explored shows that, while this substance may 
occur in any stratified rocks, of almost any geological age 
since the Cambrian, the petroleum in a single area is confined 
to. a definite bed, whose depth from the surface and probable 
extent can be predicted with considerable accuracy. Taking 
our eastern fields as a basis, since they are so much better 
explored and understood, it is found that, in a single produc- 
ing field, the oil occurs in more or less restricted areas or 
" pools," and that the pools in the Pennsylvania-New York 
district are more or less linear in extent, with their longer 
axes in general parallelism with the axes of the Appalachian 
folds. 

In distribution and behaviour the oil has a certain resem- 
blance to underground water. This resemblance is noticed 
in the tendency of these substances to accumulate in porous 
strata bounded, above and below, by more impervious layers. 
Where these strata outcrop, oil sometimes oozes out at the 
surface, like a spring of water. When a well is drilled 
into an oil-bearing stratum, the petroleum rises to the sur- 



PETROLEUM, NATURAL GAS, AND ASPHALTUM. 343 

face, after the manner of an artesian well, and at times, 
single wells produce many thousands of barrels in a day. 
The resemblance ceases here, and we find that there are 
certain marked differences. A supply of underground water 
is perennial, and, year after year, an artesian well will 
continue to flow with unabated volume because the surface 
rains soak into the earth and take the place of the water 
which escapes. But the supply of oil is the accumulation 
of ages, and, when once the stratum is exhausted of its 
store, no more will come, excepting, perhaps, after a long 
period of time, when fresh supplies have been formed. 
Moreover, while the force of ejection of the oil is, in part 
no doubt, hydrostatic, as in the case of artesian wells, yet 
there seems abundant reason to believe that this force is 
in no small degree due to the expansion of contained 
gases. 

It might, perhaps, be expected that oil would accumulate 
more rapidly in mountainous regions where distillation of 
a destructive nature is in operation, such as that which 
drives off the volatile substances from coal to produce an- 
thracite. But probably this very force of metamorphism 
aids also in the distribution of these substances, chiefly 
by producing joints and fissures through which they can 
escape, imitating, in a natural way, the artificial process 
of tapping an oil pool by a drilled well. For the forma- 
tion of oil accumulations the strata must usually remain 
practically undisturbed. Under these conditions the so- 
called pools are formed, this name being given because 
the oil is distributed unequally, as if in pools. When 
such an area is reached by a drilled well, gas sometimes 
escapes, then oil, and finally salt water; but at times this 



344 ECONOMIC GEOLOGY OF THE UNITED STATES. 

order is reversed, or in some cases oil first flows, or all 
three may come at once, or only one of the three substances 
may come, from a single well, throughout its history. 
There are probably various explanations for these phenom- 
ena, and several theories have been advanced to account 
for them. 

If the three substances are accumulated in a stratum, 
it is natural to expect that they will be stratified according 
to their specific gravity, the gas at the top and the salt 
water at the bottom. One of the old theories to account 
for the accumulation of these substances into pools or 
limited areas and for their irregularity of escape, is the 
Cavern Theory. This assumes that the gas, oil, and salt 
water have accumulated in subterranean caverns, of irreg- 
ular form, and that they occur in layers, the gas at the 
top, then oil, and finally salt water at the bottom. If the 
arch of the cavern be pierced by the well, the order of 
flow will be gas, then oil, and finally salt water ; but if 
one end be encountered, near the lower levels of the cavern, 
salt water will first escape, while oil will come first if a 
point a little higher up on the sloping side of the cavern 
be encountered. There is very little reason to believe that 
this theory is applicable, and good reasons for doubting 
its value, for it is highly improbable that such caverns exist, 
particularly in a bed of sandstone or conglomerate, where 
caverns would be difficult of formation. Moreover, the 
well-borings show no signs of large cavities. 

Recently the Anticlinal Theory 1 has been brought into 
prominence by the rapid development of the oil fields of 

1 I. C. White, The Mannington Oilfield and the History of its Develop- 
ment, Bull. Geol. Soc. Am., Vol. 3, 1892, pp. 187-216. 



PETROLEUM, NATURAL GAS, AND ASPHALTUM. 345 

West Virginia, which have been opened, in part, upon the 
basis of predictions made in accordance with this theory. It 
is, briefly, that beyond the main folds of the Appalachians 
the strata, on the bordering plateau at the western base of 
these mountains, were thrown into a series of waves or folds 
of slight elevation, and that the oil, furnished by the decom- 
position of organic remains, tending to accumulate in the 
porous strata, found it possible to accumulate in the highest 
parts of these strata ; namely, in the crests of the low anti- 
clines, while the intervening troughs or synclines were left 
barren, or nearly so. Gas would rise to the extreme crest, 
while oil and salt water would be found on the outside at a 
slightly lower level. This theory accounts for the general 
parallelism of the fields to the axes of the Appalachian folds, 
for their limited extent and distribution, and, indeed, for all 
the general features exhibited. 

There can be little doubt that the anticlinal theory is 
proved, so far as the West Virginia fields are concerned, and 
also that it accounts for some of the fields in Pennsylvania ; 
but there is good ground for doubting whether it can be 
extended to all of these fields. Some of the oil pools appear 
to be due to original irregularities of the oil-bearing stratum. 
These strata are of marine origin, and it is a familiar fact 
to be observed in all sediments from water, whether on the 
seashore, lake shore, or river banks, that they vary in char- 
acter from place to place. Thus, on a beach the material is 
pebbly in one place and sandy in another, and the same 
stratum may be sandy near shore and clayey off shore. 
Moreover, the sediments deposited opposite the mouths of 
rivers differ from those formed in the intervening areas. 
Therefore a horizon, such as one of the oil-bearing sands, 



346 ECONOMIC GEOLOGY OF THE UNITED STATES. 

may vary markedly in even a small area. Perhaps the 
texture varies, or possibly more iron or lime were furnished 
in one place than in another, and this would allow some 
parts of the bed to become firmly and compactly cemented, 
while other portions remained loose and pervious. The 
stratum, below or above, which furnished the oil may have 
varied in its ability to supply the petroleum, and in one or 
all of these ways there may very well have been a marked 
variation in either the supply or the concentration of the gas 
or the oil, thus causing an accumulation into limited areas, 
pools, or pockets, and this theory may be called the Pocket 
Theory. 

The essential features of an oil pool are a source of supply 
and a porous stratum bounded above and below by more 
impervious strata. The source is some neighbouring layer 
rich in organic remains, and the porous stratum acts as a res- 
ervoir. The exact mode of accumulation may vary, the 
organic material being changed to oil and gas by a process 
of slow distillation, and gathered into the reservoir, which 
may be a porous pocket in an irregularly porous stratum, or 
else in the crests of low anticlines. This has been written 
with especial reference to the Appalachian oil fields; but, 
while the general remarks hold for some other fields, they 
cannot be extended to those of California. There, however, 
as probably also in all other oil fields, the source of supply is 
organic remains, although the exact mode of accumulation is 
different. 

Uses of Petroleum. — The remarkable growth of the kero- 
sene oil trade, as the result of the discovery of our large 
stores of petroleum, is a matter of history with which we are 
all familiar. In 1892, 54,291,980 barrels (of 42 gallons) of 



PETPOLEUM, NATUPAL GAS, AND ASPHALTUM. 347 

crude petroleum were produced in this country, and of this, 
36,545,634 barrels were used in the manufacture of illumi- 
nating oil, while 17,676,212 barrels were used as fuel oil, 
and 70,134 barrels for lubricating purposes. Wonderfully 
expensive methods of piping are employed for the transpor- 
tation of this oil to distant points and also for its reduction ; 
but because of the great scale upon which these operations 
are conducted, these methods are economical. This has 
created an industry in which the United States holds almost 
a unique position. Not only is our home demand fully sup- 
plied, but the products of the petroleum industry find their 
wslj into nearly all the markets of the world. In 1891, 
531,445,099 gallons of illuminating oils, valued at 134,879,759, 
were exported from this country, and over $11,000,000 worth 
of other products made from petroleum were also exported. 

Aside from the production of illuminating and lubricating 
oils, the product of some districts is used chiefly for local 
fuel. During the reduction of petroleum to illuminating 
oils, naphtha, benzine, and gasoline are formed ; and a solid 
residuum of the paraffin series, used in the manufacture of 
vaseline and other similar materials, is also produced. All 
of these substances are manufactured for export as well as 
for the home market. Petroleum must be classed with coal 
and iron as one of the most important mineral products of 
the country and one which has added largely not only to our 
industrial progress, but also to the comforts of living. 

Production of Petroleum. — Statistics for the production of 
petroleum in foreign countries are difficult to obtain, but the 
following tables show the distribution of the output in this 
country, and, in a very general and incomplete manner, in 
the foreign nations : — 



348 ECONOMIC GEOLOGY OF THE UNITED STATES. 



PRODUCTION OF PETROLEUM IN THE UNITED STATES. 
Barrels (42 Gallons). 



States. 


1860. 


1870. 


1876. 


1880. 


1885. 


1888. 


1890. 


1892. 


Pennsylvania ) 
and New York > 


500,000 


5,260,745 


8,968,906 


26,027,631 


20,776,041 


16,488,668 


28,458,208 


32,080,000 


Ohio .... 


1 


31,763 


38,940 


650,000|10,010,868 


16,124,656 


20,000,000 


"West Virginia . 


.... .... 


120,000 


179,000 


91,000 


119,448 


492,578 


1,000,000 


Colorado . . . 


1 

.... | .... 








297,612 


368,842 


700,000 


California . . 




12,000 


40,552 


325,000 


690,333 


307,360 


485,000 


Indiana . . . 














63,496 


70,000 


Total for the j 
United States ' 


500,000 


5,260, T45 


9,132,669 


26,286,123 


21,847,205 


27,612,025 


45,822,672 


54,344,500 



In 1859, which was the first year of petroleum production, 
2000 barrels were produced, and, from this time till the close 
of 1862, it is believed that fully 10,000,000 barrels of oil ran 
to waste in the Pennsylvania field, because there was no 
market for it. From 1859 to 1882, the output of Pennsyl- 
vania increased rapidly, the production in the latter year 
amounting to 30,053,500 barrels. There was then a period 
of exhaustion of old wells and a failure to open extensive 
new fields, which culminated in the very low production of 
1888. Since then the discovery of new pools has caused a 
marked increase in the output, until, in 1891, the highest 
output ever reached, over 34,000,000 barrels, is recorded. 
Very nearly the same variations appear in the table of total 
output, since, until 1887, the production of the country was 
practically that of the Pennsylvania-New York field. The 
remarkable increase of output since 1887 is attributable, in 
large measure, to the development of the Ohio fields and 
the discovery of the new pools in Pennsylvania, although 






PETROLEUM, NATURAL GAS, AND ASPHALTUM. 349 

the other oil-producing states have helped this increase 
slightly. 

At the close of 1891 the United States had produced, since 
the opening of the first well, 508,447,362 barrels of crude 
petroleum, of which 429,755,990 barrels, or 84.5 per cent of 
the total, came from the Pennsylvania-New York fields, and 
64,377,499 barrels, or 12.7 per cent, from Ohio, these three 
states together having produced 97.2 per cent of the output 
of the country. In 1891, the Pennsylvania-New York field 
supplied 60.8 per cent; Ohio, 32.7 per cent; and West Vir- 
ginia, 4.4 per cent, of the total output of the country. 

PRODUCTION OF PETROLEUM IN THE WORLD. 
Metric Tons (2204 Lbs.). 



Countries. 


1889. 


1890. 


1891. 


United States . . . 

Russia 

Germany 

Peru 

Canada 1 

Italy 

Japan 1 


4,925,647 

3,306,814 

9,519 

2,151 

639,991 

177 


6,418,765 

3,974,531 

15,226 

2,324 

765,029 

417 

48,027 


7,595,702 
4,000,0002 
15,315 

755,298 
1,155 
.... 



The value of the crude petroleum produced in the United 
States in 1892 was 130,229,128. 



Natural Gas. 
General Statement. — In general, the description of petro- 
leum applies to natural gas< It belongs to the group of 

1 Barrels. 2 Estimated. 



350 



ECONOMIC GEOLOGY OE THE UNITED STATES. 



hydrocarbons and is a member of the paraffin series. Marsh 
gas constitutes from 50 to 90 per cent of the Pennsylvania 
gas, and with this there is nitrogen, carbonic dioxide, and 
some other gases. The following analyses will give an idea 
of the chemical composition of some of the natural gases : — 

ANALYSES OF NATURAL GAS. 



Pennsylvania. 

Very little. 
Paraffins, 84.26-97.7. 

Less than 1 per cent. 

Trace 

2-15. 

Trace. 



Hydrogen . . 
Marsh gas . . 
Olefiant gas 
Carbonic dioxide 
Carbonic acid . 
Oxygen . . . 
Nitrogen . . . 
Sulphuretted hydrogen 



FlNDLAY, 

Ohio. 


fostoria, 
Ohio. 


Saint 

Mary's, 

Ohio. 


Stockton, 1 
California. 


1.64 


1.89 


1.74 


0.06 


93.35 


92.84 


93.85 


83.00 


0.35 


0.20 


0.20 




0.41 


0.55 


0.44 


0.05 


0.25 


0.20 


0.23 




0.39 


0.35 


0.35 


0.06 


3.41 


3.82 


2.98 




0.20 


0.15 


0.21 





The geological distribution of natural gas very closely re- 
sembles that of petroleum, it being widely distributed through 
the strata from the early Palaeozoic to the present. Marsh 
gas, which is very similar to this, is being formed at present 
in swamps by the decay of vegetation. In Pennsylvania the 
natural gas is found chiefly in the Upper Carboniferous, in 
Ohio in the Trenton limestone, and more rarely and less 
abundantly in local reservoirs in the drift. As in the case 
of petroleum, a porous rock, with impervious enclosing strata, 
is the common reservoir, and the reason for this is the same 
in both cases. There is also a frequent association of gas 
with low anticlinal crests ; and, while it is frequently found 



Incomplete. 



PETROLEUM, NATURAL GAS, AND ASPHALTUM. 351 

free from association with petroleum, this association is not 
uncommon. Natural gas has been found in nearly all the 
states and territories, but the most important sources are 
western Pennsylvania and New York, northwestern Ohio, 
and eastern central Indiana. The origin of this gas is the 
same as that of petroleum, the one being a gaseous, the other 
a liquid, representative of the paraffin series of which paraffin 
wax is the best known illustration of the solid form. 

Natural gas was known to exist in the very earliest days 
of the exploration of western New York, where it escaped 
from crevices in the rock. In 1821 a well was drilled at 
Fredonia, Chautauqua County, New York, and gas for light- 
ing purposes was obtained. Other wells were found later, 
in the same region, and in 1841 natural gas, which had 
long been known to exist in Virginia, was introduced into 
the manufacture of salt for purposes of evaporation. Gas 
was also found to exist in association with the salt in salt 
wells, but the most important development of the gas fields 
has come since the discovery of petroleum in 1859. The ex- 
tensive drilling for oil, which has been carried on all over 
the Union, has succeeded in developing gas fields, not only 
in association with petroleum, but also in regions where this 
substance is not found. Since 1880 gas has become an 
important factor in and near the oil fields. 

Aside from the sources of this substance above mentioned 
(Pennsylvania, Indiana, Ohio, and New York), some is also 
produced in Kentucky, West Virginia, California, and, in still 
smaller quantities, in other states. Outside of the first four 
states there are very few uses for natural gas, and the indus- 
try of its production is therefore not as well developed as 
the quantity of this substance would seem to warrant. The 



352 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Ohio field has been found to extend into Ontario, and consid- 
erable is produced in this province. In China, also, wells have 
been bored, and large stores found, and natural gas has been 
discovered in other places ; but there is more of this substance 
in the United States than in any other country in the world. 
When gas is first found, it issues from the wells with tre- 
mendous force, under the pressure of the strata and of its own 
compression. Four wells in the Findlay gas region each pro- 
duced over 1,000,000 cubic feet per day, and one, the Karg 
well, produced, at first, over 12,000,000 cubic feet per day. 
Some wells have had a pressure of 800 pounds to the square 
inch, and many have a pressure of from 400 to 500 pounds. 
The Findlay wells, when first found, in 1885, had a pressure 
of 450 pounds to the square inch, in 1886, 400 pounds, in 
1889, 250 pounds, and in 1890 as low as 170 pounds to the 
square inch. These figures show that the gas wells are by 
no means permanent. Since 1888 the pressure, and conse- 
quently the output, of the great wells has been decreas- 
ing, and some which at first seemed inexhaustible are 
rapidly approaching the end of their productive days. The 
companies producing gas have recognized the probable fate 
of the industry, and are applying much more economical 
methods of using and distributing it. Already the natural 
pressure has been supplemented in some wells, by pumping, 
and, where this has been introduced, it will continue the gas 
supply a little longer; but, in general, it is a last resort em- 
ployed in a nearly exhausted well. This failure of supply 
is exactly what was predicted by those whose studies of the 
gas and oil fields forced them to the conclusion that these 
substances were simply stored in the rocks, and not continu- 
ously supplied, as some well-owners believed. 






PETROLEUM, NATURAL GAS, AND ASPHALTUM. 353 

Uses of Natural Gas. — When first found, the natural gas 
was of very little use, and immense quantities were allowed 
to escape. Its value soon became recognized, however, and 
efforts were made to introduce it for fuel and for illuminat- 
ing purposes. This is still practically the only use of gas, 
although it is also used in the preparation of lampblack 
for the manufacture of the carbon-points for electric arc 
lamps. Aside from the latter use natural gas is of im- 
portance only locally, and this is the first substance dis- 
cussed of which this is true. It cannot be exported, nor 
can it be conducted to any great distance from the wells. 

As a fuel, natural gas is used for heating and cooking, in 
the manufacture of iron and steel, for glass manufactur- 
ing, and, indeed, for scores of purposes where cheap fuel 
is needed. Gas has been so successfully introduced for 
these purposes, in the region near its source, that espe- 
cially prepared burners are introduced, and very little waste 
is now experienced; but, with the approaching exhaustion 
of the wells, serious problems are about to be presented ; 
and, indeed, already some of the companies are refusing 
to supply large manufactories with this fuel. Probably 
new fields will be discovered, but it is hardly likely that 
in the old regions many important new ones will be found. 
Little by little the industry must fail; for, unlike most 
industries, this is dependent entirely upon local and com- 
paratively limited supplies ; and, while an iron foundry, 
by the transportation of iron from other fields, might survive 
the exhaustion of neighbouring iron mines, this is not possible 
in the gas industry. 

The following table shows the various uses for which gas 
was employed in 1889 : — 



354 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



CONSUMPTION OF NATURAL GAS IN THE UNITED STATES, 1889. 

Cubic Feet. 

Various industrial establishments : brick and pot- 
tery burning, electric plants, machine shops, 

foundries, etc. , 2360 establishments in all . . 236,900,000 

Iron and steel mills 171,500,000 

Heating and cooking 62,500,000 

Drilling and operating oil and gas wells .... 30,000,000 

Miscellaneous uses 25,000,000 

Glassworks 18,750,000 

Pumping oil 7,500,000 

Total 552,150,000 

Production of Natural Gas. — There is very little basis for 
an exact estimate of the production of this substance, since so 
much is wasted, and so many different ways are made use of, 
by the various companies, for measuring their production. 
The current method of estimating the natural gas output 
is to state the value of the coal which it has displaced ; but 
this sometimes underestimates and sometimes overestimates 
the value of the production. The following tables are based 
upon this method of estimate, combined with the known 
amount received by some of the companies : — ■ 

PEODUCTION OF NATUKAL GAS IN THE UNITED STATES. 



States. 


1885. 


1887. 


1888. 


1889. 


1891. 


Pennsylvania . . 


$4,500,000 


$13,749,500 


$19,282,375 


$11,593,989 


$7,834,016 


Indiana .... 




600,000 


1,320,000 


2,075,702 


3,942,500 


Ohio 


100,000 


1,000,000 


1,500,000 


5,215,669 


3,076,325 


New York . . . 


196,000 


333,000 


332,500 


530,026 


280,000 


Kentucky . . . 








2,580 


38,993 


"West Virginia . . 


40,000 


120,000 


120,000 


12,000 


35,000 



PETEOLEUM, NATURAL GAS, AND ASPHALT UM. 355 

In 1889, Pennsylvania produced over one-half of the supply 
of the country, Indiana about one-fourth, and Ohio nearly one- 
fifth ; or the three states together about nineteen-twentieths 
of the supply of the country. The rapid increase in Pennsyl- 
vania's output, which reached a maximum of over $19,000,000 
in 1888, followed by a rapid decline, is a noteworthy feature 
of the table. Ohio has also rapidly increased its output, 
and this has been followed by a decline, while the Indiana 
output has gradually increased. 

NATURAL GAS PRODUCTION OF THE UNITED STATES. 

1882 $215,000 

1883 475,000 

1884 1,460,000 

1885 4,857,200 

1886 10,012,000 

1887 15,817,500 

1888 22,629,875 

1889 21,097,099 

1890 18,742,725 

1891 15,500,084 

1892 13,000,000 

Before 1882 much gas was produced, but it was practically 
all wasted. The wonderful increase from 1882 to 1888 and 
then the continuous and rapid decrease to the present time 
are very striking features of the table, and these variations 
are primarily due to Pennsylvania. The value of the natural 
gas produced in Canada, in 1892, was 1160,000. 

Asphaltum. 

Certain semi-solid bitumens, varying slightly in character, 

and to which different mineralogical names 1 are given, are 

1 The names of the various varieties are albertite, asphaltum, brea, 
elaterite, gilsonite, grahamite, lithocarbon, maltha, uiutite, and wurtzilite. 



356 ECONOMIC GEOLOGY OF THE UNITED STATES. 

included under the general term of asphaltum. In this 
country, as in many others, bituminous shales and limestones 
with very small percentages of bitumen are not uncommon, 
and some of them are sufficiently bituminous to be employed 
directly, in place of prepared asphalt, 1 while others are used 
as a source of asphalt. Bituminous sandstone is quarried 
extensively in Kentucky and California, while in Utah a 
bituminous limestone is used for a source of asphalt; and 
in this territory there is also found a variety known as gil- 
sonite. Recently an extensive deposit, which is called litho- 
carbon, has been discovered in western Texas, but as yet 
there has been no output. Other deposits are known to 
exist elsewhere in this country, but at present they are 
of little importance. The chief supply of the asphalt 
used in the United States comes from the island of Trin- 
idad, where the famous pitch lake occurs; but other re- 
gions, notably Sicily, also produce asphaltum. 

The origin of this substance is, in some places at least, from 
organic remains, by a slow process of distillation similar to 
that which produces petroleum. In the bituminous lime- 
stones and shales, bitumen, instead of petroleum, has resulted 
by the concentration of the solid parts and the dissipation 
of the volatile portions. This has resulted, in the sedimentary 
strata, from slow distillation ; but, in the neighbourhood of 
igneous rocks, it may have been caused by destructive dis- 
tillation. The resemblance between this mineral and petro- 
leum is shown by the fact that in the California petroleum 
the solid base is a form of asphaltum. It has been suggested 
that the stages of change are first the transformation of 

1 The term asphaltum is given to the unfinished product, and asphalt is 
the commercial name for the finished product used in street-paving. 



PETROLEUM, NATURAL GAS, AND ASPHALTUM. 357 

organic remains to oil, then to asphaltum, next to jet, and, 
finally, under sufficient metamorphism of the proper nature, 
to diamond. While this is purely hypothetical, it is not 
improbable. The chemical composition is closely like that of 
parts of some petroleums, and the California petroleum has 
asphaltum for a base. Products closely resembling asphaltum 
can be produced artificially. 

This substance is employed, in the form of asphalt, for 
paving streets, and this is by far its most important use ; 
but it is also made use of as a varnish for coating piles and 
wharf timbers. 

PRODUCTION OF ASPHALTUM IN THE UNITED STATES. 

Year. Short Tons. Value. 

1880 444 $4,440 

1885 3,000 10,500 

1890 40,841 190,416 

1892 54,985 291,250 

Owing to the cost of transportation, the greater part of 
the asphaltum produced in the United States cannot com- 
pete with that shipped from Trinidad and elsewhere, and 
our supply is consequently used chiefly near the point of 
production. In 1892, while we produced 54,985 tons, our 
imports amounted to 109,582 tons, the greater part of which 
came from Trinidad. 

Ozokerite. 

A mineral belonging to this series is mineral wax or 
ozokerite (ozocerite), which occurs in Galicia, in Austria- 
Hungary, but which has also been found near Thistle in 
Utah. It is a yellow mineral, grading to a dark brown, 



358 ECONOMIC GEOLOGY OF THE UNITED STATES. 

sometimes greenish, and varies in hardness from very soft 
to the hardness of gypsum. It may be considered an altered 
form of a petroleum, robbed of its volatile substance, and 
more nearly resembling that of Pennsylvania than that of 
California. It is chiefly a solid paraffin with some ben- 
zine, naphtha, etc. The uses of this mineral are, as a 
substitute for beeswax, in the manufacture of candles, for 
purposes in which vaseline is employed, and as an insulator 
in electricity. Before 1888, when ozokerite was discovered 
in Utah, Galicia was the source of this mineral, which was 
first obtained there in 1862. Our product, in 1892, was 
130,000 pounds, valued at 17800, while we imported 
1,250,000 pounds. The industry of mineral wax produc- 
tion is slowly increasing. 



CHAPTER XVI. 

BUILDING-STONES AND CEMENTS. 

Building- Stones. 1 

General Statement. — The non-metallic structural materials 
may be divided into four groups, — building-stones, ornamental 
stones, natural and artificial cements, and clays. All but the 
last of these are included in this chapter, the clays being 
omitted here, since a very important use for these substances 
is the manufacture of pottery and ornamental ware. Gypsum, 
which is also used for structural purposes, is omitted here, 
but is considered under fertilizers, since this is one of the 
most important uses of the mineral. Under building-stones 
is included the limestone burned and used for fertilizing pur- 
poses, and that, also, which is burned for lime to be used in 
plaster. For the term building-stones a more comprehen- 
sive word might be substituted, since under this heading is 
included, not only the stones used for building, but those 
also quarried for other structural purposes, such as pave- 
ments, fences, bridges, monuments, etc. ; but, although this 
is perhaps a poorly chosen term, it is employed here because 
it is in common use in the statistical works. 

Practically, none of these products are of value for expor- 

1 The general subject of building- stones is treated by Merrill in his Stones 
for Building and Decoration, New York, 1891 ; and, in this connection, 
Burnhain's Limestone and Marble will be found of value. The Tenth Cen- 
sus volume on Building-stone is also of value. 

359 



360 ECONOMIC GEOLOGY OF THE UNITED STATES. 

tation, but nearly every country, and, in our own country, 
nearly every section, produces its own supply. Thus, in 
regions of granitic rocks, granites are commonly used, while 
in sandstone regions, buildings and other structures are 
more commonly made of this stone than of any others. Only 
the very finest quality of stone is capable of profitable trans- 
portation, and hence we neither export nor import any but 
the best, usually ornamental stone. Where particular kinds 
and colours of marble are desired for interior decoration, or 
certain granites or marbles are needed for monuments, these 
are imported in some cases ; but the amount of these im- 
portations is very small, being greater for marble than for 
any other stone. Even within the country there is a very 
small amount of distant transportation. Certain colours of 
stone, needed for trimming, may be carried long distances 
where a particularly beautiful building is to be constructed ; 
and where cheap transportation by water is possible, even 
paving-blocks may be carried several hundred miles; but, 
notwithstanding these exceptions, the industry of building- 
stone production is essentially a local one. If statistics were 
obtainable of the distribution of the stone product which 
is actually sold, this would be found to be very marked, 
but not nearly so striking as it really is, since large quanti- 
ties of stone used for structural purposes are never put upon 
the market, but are quarried by the consumers. For this 
very reason the statistics of building-stone production, as 
given below, are far below the actual value of the industry. 

Granite. — Under the term granite, as used in the trade, 
is included a great variety of igneous and metamorphic 
rocks, among which are the true granites; and these, it is 
true, form the greater part of the so-called granites. Normal 



BUILDING-STONES AND CEMENTS. 361 

granite, using the term in its strict scientific sense, is an 
igneous rock intruded at considerable depth into the earth, 
hence a plutonic rock, having a coarsely crystalline structure 
and being made up of a granular, interlocking series of 
quartz, orthoclase, feldspar, and grains of either hornblende 
or mica (usually biotite), sometimes both. Other minerals 
are present, usually in minor quantities, and as accessories. 
The coarseness of texture varies greatly from an extremely 
fine grain to a very coarse rock ; and, indeed, some granites 
are entirely too coarse for use. The colour is also extremely 
variable, some being almost white, others a very dark green, 
some blue, and some red. These colours depend in cer- 
tain cases on the proportion of the constituent minerals, 
but most commonly upon a pigment contained in the feld- 
spars. Even in the same rock some of the feldspars are red, 
while others are white, and just what these pigments are is 
not always easy of determination. It is sometimes minute 
grains of iron and often a series of microscopic inclusions of 
some coloured mineral. 

Different kinds of granite are used for different purposes. 
For monuments and ornamental work there is an. especial de- 
mand for coloured granite, generally of fine grain, which fits 
it for polishing ; but in many of the uses for which granite is 
employed the colour is of minor importance, durability, hard- 
ness, and cheapness (the latter depending upon the ease of 
working it) being of prime importance. This stone occurs in 
large masses almost entirely in the older rocks, and very com- 
monly in the metamorphic series. This is one reason why 
New England is of so much importance in the production of 
granite ; but it is also necessary that the rock shall be so 
situated that it can be easily quarried and transported at a 



362 ECONOMIC GEOLOGY OF THE UNITED STATES. 

slight cost to a good and permanent market. Thus it is that 
so many quarries are situated on or near the seashore where 
water transportation is possible. 

Another important feature in granite is to have its texture 
and colour moderately uniform, and many very beautiful 
stones are rendered of little value, for most purposes, by 
reason of frequent inclusions or bunches of darker coloured 
minerals, which give to the rock a blotched surface. These 
bunches are, in some cases, actual inclusions of some other 
rock torn off from the country rock, when the granite was 
forced in a molten condition through the strata into its pres- 
ent position. These are partly melted and merged into the 
granite, but the centre is frequently very little changed and 
forms a marked contrast to the stone. Even more common 
than these are the dark bunches known as basic secretions, 
which are accumulations of the darker minerals of the rock 
into bunches by a process analogous to concretion, which 
operates while the rock is cooling from the igneous condi- 
tion. Thus, hornblende, biotite, magnetite, and other basic 
minerals, gather together into bunches which are frequently 
so abundant that it is impossible to obtain a slab which is 
free from them. In some granites, particularly the coloured 
and darker kinds, these are very abundant, while in the 
lighter granites they are often nearly absent; and even in 
the same quarry there is considerable variation in the abun- 
dance of these patches. 

Granite is an extremely hard and durable rock. The 
quartz which it contains, although brittle, and thus affect- 
ing its crushing strength, is practically indestructible, and 
feldspar normally weathers slowly and does not seriously 
injure the rock. It is also nearly as hard as quartz and 





VI 



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Ct 



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o 

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o t: 



BUILDING-STONES AND CEMENTS. 363 

somewhat less brittle. The weakest parts of the stone are 
the basic minerals, chiefly the biotite, hornblende, and mag- 
netite, which are generally in less abundance than either 
the quartz or feldspar. Under the influence of the weather 
these begin to decay to other minerals, of which the oxides of 
iron are the most prominent. It is this which causes the red 
stain or rust upon joint planes, sometimes extending into the 
rock for a distance of several inches. Quarrymen call this 
the " sap," as if it were rising from the granite and passing 
out, while in reality it begins at the surface of the joints and 
slowly extends inward as fast as the percolating water can 
effect the necessary changes in the minerals. At first this 
does not materially weaken the rock, although it soon com- 
bines with other changes, particularly the kaolinization of 
the feldspar, and causes the granite to crumble. For a long 
time this "sap" stain was believed to ruin the stone, but 
recently it has been introduced into buildings; and, when 
the main part of the structure is composed of this rusted 
rock, trimmed with a lighter coloured stone, a very beauti- 
ful building is constructed. Instead of being thrown away, 
as it has been in the past, this rusted granite, because it is 
comparatively scarce, promises soon to become one of the 
most valuable products of the granite quarry. 

This rock is so hard that but for the presence of planes 
of mechanical weakness it could not be utilized for many 
purposes for which it is now so valuable. These planes 
are of two kinds, — joint planes and microscopic planes (rift), 
along which the rock tends to split. There are ordinarily 
four sets of joint planes in a granite quarry (Plate II.) . 
One of these is a nearly horizontal jointing, which some- 
times assumes an angle of 15° or 20°, and is the result of 



364 ECONOMIC GEOLOGY OF THE UNITED STATES. 

the contraction of the rock during cooling. By this set 
of joints the granite is traversed at various intervals, the 
divisional planes forming dome-shaped blocks with a radius 
of many yards, sometimes of several hundred feet. In 
some quarries the joints of cooling are so numerous that 
large blocks cannot be extracted ; but in others, where the 
horizontal joints are several yards apart, it is possible to 
obtain immense blocks of the granite. The other three 
sets are nearly vertical, two of them meeting at an angle 
approaching a right angle, while the third cuts diagonally 
the rhomboidal blocks thus formed. These are joint planes, 
partly of contraction, partly of mechanical origin, the re- 
sult of folding and crushing of the granite during sub- 
sequent movements of the rocks. As in the case of the 
nearly horizontal joints, there is great variety in the num- 
ber of the planes of breakage, and while sometimes they 
are twenty, thirty, or even as much as fifty feet apart, 
in other places they cut the rock in such numbers that 
it breaks into small pieces, a veritable fault breccia, which 
ruins the granite for economic purposes. 

These joint planes are of great importance in quarrying, 
since they form bounding planes, beyond which the charge 
of powder used in blasting will not break the rock. A 
series of smooth, naturally-formed working faces are thus 
furnished, and the work of quarrying greatly facilitated. 
Near the surface the joint planes furnish channels for the 
passage of underground water ; and it is for this reason that 
their faces, and the granite for some distance in from these, 
are discoloured by iron rust ; but as the depth of the quarry 
increases, the joint planes become less numerous. This 
shows that the joints are, in some cases at least, merely 



BUILDING-STONES AND CEMENTS. 365 

microscopic planes of splitting developed by percolating 
water. The green seams which are present in many quar- 
ries illustrate this still better. These are joints, along 
which some chloritic minerals have accumulated, and which 
are called blind seams by the quarrymen when the chloritic 
minerals are absent or not present in sufficient abundance 
to be indicated on the surface of the freshly quarried rock. 
Even after the block has been blasted from the quarry, these 
seams may not be visible, and sometimes, during the final 
shaping of the stone, it splits along one of these invisible 
planes, and causes the loss of all the labour employed. 
This is not a very common occurrence, but it is interest- 
ing for the purpose of showing what joint planes prob- 
ably are. 

Even more important than the joints are the microscopic 
planes of weakness known by quarrymen as " rift." 1 Exam- 
ined with the microscope, these are shown to be microscopic 
breaks and tiny faults crossing all the minerals, but usually 
not with sufficient development to injure the strength of 
the rock. In well-rifted granites these planes of breakage 
can be seen with the naked eye ; but at times they are 
shown only when the rock is split, by a tendency to a 
smooth fracture in certain directions. There are three sets 
of smooth-fracture planes in some quarries, the most pro- 
nounced vertical plane being called the "rift"; the second, 
the "cut-off"; and the third, a horizontal plane, the "lift." 
One of the first things to be determined in opening a quarry 

1 The remarks upon rift are based upon a study of the granite in the 
quarrfes at Cape Ann, Massachusetts. So far as is known, studies of this 
phenomenon similar to those made by the author have not been carried on 
elsewhere, although rift is common in granite. 



366 ECONOMIC GEOLOGY OF THE UNITED STATES. 

is the direction of these planes, and in drilling holes for 
splitting the rock these directions are followed. The rift 
furnishes the direction for the greatest length of the block, 
the cut-off for the least important end, and the lift for 
cleaving the block upon the third side. When these planes 
are well developed, large blocks twenty or twenty-five feet 
square, and even more, are readily split from the quarry, 
with such smooth faces that very little dressing is needed 
to prepare the rock for polishing. In no class of work is 
this tendency of splitting so needful as in the preparation 
of paving-blocks, the cheapness of which depends upon the 
facility of breaking in three directions. 

Aside from granite proper, many other igneous and some 
metamorphic rocks are used as granite, and called by this name 
in the market. One of these is gneiss, a metamorphic rock, 
which, in some cases, so closely resembles a granite that only 
a careful study serves to distinguish it. This rock, however, 
frequently has a lower crushing power than granite, because 
of the presence of the gneissic structure, which is a direc- 
tion of weakness, often very marked. One of the principal 
objections to gneiss is the lack of uniformity of texture and 
colour, which, excepting in unusual cases, is not so good as 
in ordinary granites. Much gneiss, however, which is quar- 
ried and sold as granite is a really good stone which cannot 
be distinguished from a good granite by the ordinary char- 
acters of economic importance. Very nearly every igneous 
rock is quarried and sold as granite, 1 and some of them are 
not seriously inferior to true granite. Syenites, in which 
there is no quartz, are not as strong chemically, as true 

1 Upon pages 598, 599, Eleventh Census volume on Mineral Industries, 
will be found, tabulated, the various varieties of rock sold as granite. 






BUILDING-STONES AND CEMENTS. 367 

granites; but they are of better quality than many of the 
igneous rocks. The basic rocks, such as diabase and diorite, 
contain minerals which decay so readily that they are gen- 
erally unfit for exposed work. By far the greater part of 
the rock quarried and sold as granite is normal granite ; 
but since so much that is not of this species is sold 
under this name, one should, before using any other kind, 
carefully study the character of the rock, provided a use is 
to be made of it which requires durability and strength. 

Granite is employed for a variety of purposes ; and its 
value varies greatly, according to the use to which it is to 
be put and the location of the quarry. In 1889 the total 
value of the granite produced in the United States was as 
follows : — 

VALUE OF THE GRANITE PRODUCED IN THE UNITED 
STATES, 1889. 

Building purposes , $6,166,034 

Street work 4,456,891 

Cemetery, monumental, and decorative purposes, 2,371,911 

Bridge, dam, and railroad work 1,238,401 

Miscellaneous uses 230,858 

Total value $14,464,095 



This represents a total of 62,287,156 cubic feet of granite 
actually sold, but makes no allowance for a not inconsider- 
able amount quarried and used by private individuals and 
corporations, but not placed upon the market. Large quan- 
tities of granite are wasted in the course of quarrying and 
dressing operations. 



368 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



PRODUCTION OP GRANITE IN THE UNITED STATES. 



States. 


1880. 


1889. 


1891. 


Massachusetts 

Maine 


11,329,315 

1,175,286 

172,450 

407,225 

64,480 

303,086 

623,000 

59,675 

211,454 


$2,503,503 

2,225,839 

1,329,018 

1,061,202 

752,481 

727,531 

931,216 

581,870 

623,252 


$2,600,000 

2,200,000 

1,300,000 

1,167,000 

790,000 

750,000 

750,000 

700,000 

575,000 


California 

Connecticut 

Georgia ......... 

New Hampshire 

Rhode Island . 

Vermont 

Pennsylvania 


Total for the United States 


$5,188,998 


$14,464,095 


$13,867,000 



In 1891 nine states, Maryland, Wisconsin, Colorado, Mis- 
souri, New Jersey, Virginia, New York, Delaware, and South 
Dakota, named in the order of their importance, produced 
more than $100,000, and less than $500,000, worth of gran- 
ite. It will be noticed that all the New England states are 
included in the first eight granite-producing states of the 
Union, this being the first economic product in which any 
one of them has held a high rank. During the year 1891, 
$8,167,000 of the total output of the country came from 
these states. Nearly the entire supply came from the east- 
ern states, and the greater part of this from the states of the 
extreme east. The rapid development of the granite indus- 
try is shown in the table, but in the last year a considerable 
decline is noticed. Particularly striking is the development 
of the industry in Georgia, Vermont, California, and Con- 
necticut. 



BUILDING-STONES AND CEMENTS. 369 

Sandstone. — Sandstone, being a sedimentary rock, will 
naturally be found where sedimentary strata abound; and in 
our country these conditions are most markedly developed 
in the central states. None is found in the metamorphic 
region, excepting in isolated basins, where later rocks have 
accumulated, as in Connecticut. Very little is produced in 
the Cordilleras, but less because of its absence than by rea- 
son of the difficulty of finding a market for it. 

The geological age is very variable, and sandstones are 
found in all sedimentary strata from the Cambrian to the 
Tertiary; but the greater part of our supply comes from the 
Palaeozoic in the central states and the Triassic in Penn- 
sylvania (in part), New Jersey, and Connecticut. 

The rock is composed of grains of sand, usually of quartz 
sand, with some feldspar, mica, etc., cemented, sometimes by 
silica, but more commonly by iron or by carbonate of lime. 
It is, therefore, a very good building-stone, provided the 
grains are firmly cemented. Usually the crushing power is 
not great ; but owing to the abundance of quartz, the chemi- 
cal durability is very marked. If the cement is silica, the 
rock is as durable as any common rock can be ; but such 
sandstones, or quartzites, are not commonly used, because of 
the difficulty of quarrying and dressing so hard a rock. With 
a firm lime or iron cement the stone is sufficiently durable for 
ordinary purposes ; but even in such cases, and much more 
markedly when the cement is not firm, water dissolves the 
cement, and forms crevices, which heat and frost expand, 
causing the grains of sand to fall apart and the stone to 
crumble. The effect of weathering is very well shown in 
many old buildings made of sandstone ; but there are such 
buildings, many centuries old, which are sufficiently well 



370 ECONOMIC GEOLOGY OF THE UNITED STATES. 

preserved for use at present. It is not as durable as good 
granite, but is one of the best building-stones. 

In the texture there is great variability, though this is not 
as marked as in granite ; for, when the grain is coarse, the 
rock is a conglomerate, and, ordinarily, this stone is not 
suited for building purposes. From this extreme, sandstones 
grade to a very fine-grained rock; and some of these are 
almost clay rocks, being, properly speaking, argillaceous 
sandstones. The colour is also variable : blue or green, in 
shades of varying intensity, as well as red, pink, brown, 
and white being the most common; but in the sandstones 
there is an almost infinite variety of colouring. According 
to the localities from which the stone is obtained, and fre- 
quently to the colour or texture, various commercial names 
are employed, such as blue or buff Amherst (Ohio) sand- 
stone ; Portland (Connecticut) brownstone ; freestone, a 
name given to sandstones which may split easily or freely 
in various directions ; Berea (Ohio) grit, etc. 

The method of quarrying sandstone varies greatly, accord- 
ing to the locality and character of the stone ; but, in all 
cases, the fact that it is a sedimentary rock aids the quarry- 
ing, by giving one direction of easy splitting parallel to the 
bedding. Where the strata are thick bedded, that is, with 
the parting planes of stratification far apart, it is often pos- 
sible to obtain large blocks ; but in this case the quarrying 
operations are more difficult, and blasting is resorted to for 
the purpose of breaking the rock across the bedding. In 
thin-bedded sandstones channelling-machines are employed 
to cut from layer to layer, and, in some of the Connecticut 
brownstone quarries, the rock is grooved with pickaxes, and 
then split by driving wedges at intervals in the grooves ; but 



BUILDING-STONES AND CEMENTS. 371 

this is possible only when the rock is soft. In all quarrying 
operations vertical joint planes are of great service, and this 
is true of sandstones as well as of other rocks. These joints 
prevail throughout all strata, although they are sometimes 
absent. 

The value of sandstone varies greatly with the colour, 
texture, and the demand for particular kinds. During the 
census year 1889, 71,571,054 cubic feet of sandstone were 
quarried and sold for the following purposes : — 

VALUE OF THE SANDSTONE PRODUCED IN THE UNITED 
STATES, 1889. 

Building purposes $7,121,942 

Street work 1,832,822 

Bridge, dam, and railroad work . . . 1,021,920 

Abrasive purposes 580,229 

Miscellaneous 259,144 

Total for all purposes $10,816,057 

PRODUCTION OF SANDSTONE IN THE UNITED STATES. 



States. 


1880. 


1889. 


1891. 


Ohio 

Colorado 

Connecticut 

Pennsylvania 

New York 


$1,871,924 

9,000 

680,200 

627,943 

724,556 


$3,046,656 

1,224,098 

920,061 

1,609,159 

702,419 


$3,200,000 
750,000 
750,000 
750,000 
500,000 


Total for the United States 


$4,780,391 


$10,816,057 


$8,700,000 



The bluestone industry is included in the statistics for 
1880 and 1891. A marked increase is noticed in the produc- 



372 ECONOMIC GEOLOGY OF THE UNITED STATES. 

tion of the country and of some of the states, notably 
Colorado and Ohio, between 1880 and 1889, and a marked 
decline, from 1889 to 1891, in the production of all the 
states, excepting Ohio, which is pre-eminently the sandstone- 
producing state of the Union. Seven states, Wisconsin, 
Massachusetts, New Jersey, Minnesota, Michigan, California, 
and Missouri, named in the order of their importance, pro- 
duced between 1100,000 and $500,000 worth of sandstone 
in 1891. 

Bluestone. — A very fine-grained variety of shaly sand- 
stone, usually of a bluish colour, and consisting of particles 
of silica and some argillaceous matter, cemented by silica, 
is included under this heading. Ordinarily in statistical 
studies this rock is included under the sandstones ; but in 
the Eleventh Census report it is given a separate considera- 
tion, because the rock differs from sandstone both in char- 
acter, and use. The stone, which is intermediate between a 
shale and a sandstone, might, with propriety, be called a 
siliceous shale. Its colour is usually a dark blue, but some- 
times it is light blue, sometimes green, and, in some cases, 
even brown. The value of the stone depends upon its fine 
texture and hardness, in part, but chiefly upon its thin- 
bedded nature, which allows it to be obtained in thin slabs 
suitable for flagging. This is its principal use, although it 
is being introduced for other purposes where thin slabs are 
needed. In the bluestone flags there are frequently pre- 
served most excellent ripple marks, which prove that when 
it was formed, shore-line conditions prevailed at the point of 
deposition. 

New York is the principal bluestone-producing state, and 
it is found there in several counties, chiefly in the central 






BUILDING-STONES AND CEMENTS. 373 

part of the state. Both Pennsylvania and New Jersey also 
produce flagstones of this type. The following table shows 
the value of the industry, but does not give returns from a 
large number of small quarries, which produce small quan- 
tities of flagging for local purposes. Many of these quarries 
are opened by farmers, and worked at intervals when farm- 
ing work is not pressing. 

PRODUCTION OF BLUESTONE IN 1889. 

New York $ 1,303,321 

Pennsylvania 377,735 

New Jersey 8,550 

Total $1,689,606 

Slate. — This rock is formed by the alteration of clay 
strata, of sedimentary origin, and the slaty cleavage is a 
new structure imposed by pressure and metamorphism, which 
have sometimes operated even to the extent of destroying 
the original bedding. The new structure, which is called 
slaty cleavage, is developed at right angles to the direction 
of the pressure, and consists in the formation of new 
minerals, chiefly hydrous and other micas, which give to it 
the shiny surface of the slate faces and the ease of splitting 
in a given direction, parallel to the faces of the mica plates, 
and dependent upon the general parallelism of these plates. 
It is an intermediate stage between clay rocks (such as 
shales) and mica schist. The sedimentary origin of the rock 
is sometimes shown by the presence of bedding planes, 
usually at an angle with the cleavage, and more rarely by the 
presence of distorted fossils. In colour the slate is usually 
slate-blue ; but there are green, brown, purple, and red 



374 ECONOMIC GEOLOGY OF THE UNITED STATES. 

slates. These shades depend upon the prevailing colour of 
the component minerals or upon some stain or pigment, the 
red and brown being due to iron, the purple to manga- 
niferous minerals, the green to chlorite, and the blue to a 
combination of chlorite, carbonaceous matter, and other 
substances. 

Slates may be of any age where metamorphism has altered 
clay rocks to the stage of slates. They are almost uni- 
versally absent from the Archean, because, if clay rocks 
ever existed there, they have passed the slate stage of meta- 
morphism and become mica schists. These rocks are usually 
absent from the strata of post-Palaeozoic age, for the reason 
that rocks of this age have not usually been exposed to 
extensive metamorphism. Still, in California the strata of 
the Sierra Nevada consist in part of slates of Cretaceous age, 
and there are more recent slates elsewhere. The Palaeozoic 
age, and of this the earliest members, is the most important 
slate-bearing series both in this country and elsewhere. 
This rock is widely distributed, but the most important states 
are situated in the Appalachian and New England regions, 
where there is a belt of Cambrian and Silurian age, extend- 
ing from Vermont to Georgia. 

The value of slate depends upon the presence of the 
remarkable cleavage which admits of its being split readily 
in a single direction so that thin sheets of moderate size can 
be obtained. In quarrying slate, joint planes are of great 
importance ; but when they are too numerous, the rock splits 
into such small blocks that slate for tiling cannot be ex- 
tracted. While this rock is extremely common, good roof- 
ing-slate is comparatively rare, because either the texture is 
not uniform, or the colour not suitable, or the cleavage not 



BUILDING-STONES AND CEMENTS. 375 

properly developed, or joint planes too numerous. Many 
slates, called argillites, have not had the slaty cleavage 
developed to a marked degree, either because of the original 
texture, or the fact that metamorphism has not been suffi- 
ciently powerful. On the other hand, some slates have such 
a shaly structure that the flakes are too thin for use ; others 
have several cleavages, which cause the rocks to split with 
an irregular surface ; and in some the bedding is not suffi- 
ciently destroyed to prevent its furnishing a second plane 
of cleavage. A good roofing-slate must be massive and 
strong, with only one cleavage, which must be well devel- 
oped; and it should have a uniform texture, a permanent 
colour, and should not be too brittle for cutting into regular 
forms. While the greater part of the slate is dark blue, the 
light blue, green, red, and other colours are used for figures, 
margins, and, in general, for relieving the monotony of a 
single colour in roofing. 

By far the greater part of the supply is used for roof- 
ing, but some is also consumed in the manufacture of slates 
for school purposes, for strips, flagging, sills, mantels, wash- 
bowls, and many minor purposes, where an easily worked 
rock of uniform texture and colour is desired. Marbleized 
stone, which is being introduced for interior work, in imita- 
tion of banded and coloured marble, is made by a process of 
graining with colours upon slate tablets and slabs. Some of 
this work is very beautiful, but the fact that it is an imita- 
tion, and not permanent, is liable to prevent its general in- 
troduction. The rapidly increasing use of metal for roofing 
is interfering with the consumption of slate for this purpose, 
particularly in the east. In 1891 the total consumption of 
slate was valued at $3,825,746, of which 13,125,410 worth 



376 ECONOMIC GEOLOGY OF THE UNITED STATES. 

was used for roofing purposes, this amount representing 
893,312 squares of slate. 

PRODUCTION OF SLATE IN THE UNITED STATES. 



States. 


1880. 


1889. 


1891. 


Pennsylvania 


$863,877 


$2,011,726 


$2,141,905 


Vermont 


352,608 


842,013 


955,617 


Maine 


83,800 


219,500 


250,000 
176,000 


New York 


95,500 


126,603 


Virginia 


51,000 


113,079 


127,819 


Maryland 


56,700 


110,008 


125,425 


Total for the United States 


$1,529,985 


$3,482,513 


$3,825,746 



Limestone. — Deposits of carbonate of lime are sometimes 
precipitated from solution, but most frequently they are 
the accumulations of animal remains, generally of coralline 
animals. By these agencies vast stores of limestone have 
been built in all geological ages, and consequently every 
part of the country produces this stone. In Florida, and 
in many oceanic islands and coral reefs, accumulations 
of recent shells and coral fragments have been loosely 
cemented, forming a coquina which is used locally for 
building purposes. This coquina differs in no essential 
particular from true limestone, excepting in the degree of 
consolidation ; and since it is being formed under our very 
eyes, it serves as an excellent illustration of the ease with 
which rocks may be consolidated when there is present an 
abundant supply of a very soluble mineral, such as calcite, 
which is the cementing material of limestone. 



BUILDING-STONES AND CEMENTS. 377 

In colour limestone varies markedly, from black to pure 
white, with abundant blues, browns, and grays. The text- 
ure varies from a very fine grained compact rock to a semi- 
crystalline, and even a very coarsely crystalline marble com- 
posed of calcite crystals. It may be nearly pure carbonate 
of lime, or a nearly pure magnesian carbonate or dolomite ; 
it may be a black carbonaceous or bituminous limestone; 
or it may pass by gradations from an argillaceous limestone 
to a limy shale ; and between these various kinds there is 
every gradation. 

Under the term limestone should properly be included 
only those rocks which are composed chiefly of carbonate 
of lime ; but commercially, siliceous, argillaceous, and mag- 
nesian limestones are all included under limestone. More- 
over, there is a peculiar complication resulting from the 
attempt to separate marble from limestone. When a lime- 
stone has been metamorphosed, the carbonate of lime 
becomes altered to crystalline calcite, and the impurities 
gather together either in bands of different colours or in 
bunches of various minerals. This results in the formation 
of true marble, which should very properly be separated 
commercially from ordinary limestone, since it is metamor- 
phosed and crystalline, and, being capable of a high polish, 
serves for purposes for which ordinary limestone cannot be 
used. But under the term marble, in its commercial 
sense, is included many non-crystalline limestones, which, 
by polishing, show either banding or some desired colour, 
such as black. Consequently marble in its commercial 
significance is made to include stone which is not true 
marble. Nor is the term limestone any more exact, since, 
not only does it include many very impure limestones, but 



378 ECONOMIC GEOLOGY OE THE UNITED STATES. 

also true marble, when this is not situated in positions 
favourable for quarrying, or has not a sufficiently fine text- 
ure, or cannot be obtained in sufficient quantities, or in 
large blocks. 

Commercial limestone may be said to be any rock contain- 
ing a sufficient quantity of carbonate of lime to pay for burn- 
ing ; and commercial marble may be defined as any limestone, 
crystalline or non-crystalline, which is susceptible of a polish, 
and has a colour and texture suitable for ornamental work, 
and a position favourable for economic extraction. The 
terms are therefore far from scientific. Properly speaking, 
marble is metamorphosed and either partly or completely 
altered limestone, usually semi or wholly crystalline. But 
since there is every gradation from one form to the other, 
it is difficult to always distinguish them, as, indeed, it is in 
the case of all sedimentary rocks, for there is every gradation 
from conglomerate to sandstone, from sandstone to shale, 
from shale to limestone, and from limestone to marble. 

In 1889 the total supply of limestone produced in the 
country was used for the following purposes : — 

USES OE LIMESTONE IN 1889. 

Lime $8,217,015 

Building 5,405,671 

Street work 2,383,456 

Flux. .' 1,569,312 

Bridge, dam, and railroad work . . 1,289,622 

Miscellaneous 230,103 

Total. . $19,095,179 

For some of these purposes it is not necessary that the 
rock should have particular qualities, but for others it should 



BUILDING-STONES AND CEMENTS. 



379 



be comparatively pure. This table does not fully repre- 
sent the value of the industry, particularly that part of 
it which is represented in the manufacture of lime, and 
that used as a flux. Full returns have not been obtained 
from many blast furnaces which quarry their own flux, 
and there are, in operation upon farms, large numbers 
of lime-kilns for burning limestone to be used either as 
a fertilizer or a plaster. These two industries should 
have their total increased; and probably the total value 
of the limestone quarried and used for all purposes is 
over $21,000,000. 

PKODUCTION OF LIMESTONE IN THE UNITED STATES. 



States. 


1880. 


1889. 


1891. 


Indiana 

Pennsylvania 

Illinois 


$593,375 
240,934 

1,320,742 
421,211 
669,723 

207,000 
189,320 
201,593 


$1,889,336 
2,655,477 
2,190,607 
1,859,960 
1,514,934 
1,523,499 
1,708,830 
813,963 
613,247 


$2,100,000 
2,100,000 
2,030,000 
1,400,000 
1,250,000 


Missouri 

Ohio 


Maine 


1,200,000 

1,200,000 

675,000 

600,000 


New York 

"Wisconsin 

Minnesota 


Total for the United States . 


$6,856,681 


$19,095,179 


$15,792,000 



The combined value of the marble and limestone indus- 
tries in 1880 amounted to only $6,856,681, while in 1889 
it exceeded $25,500,000, showing a striking increase in ten 
years. Thirteen states, California, Iowa, Alabama, Kansas, 
Kentucky, Nebraska, Texas, Vermont, Virginia, Maryland, 



380 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



Connecticut, Massachusetts, and New Jersey, named in the 
order of their importance, each produced over $100,000 
and less than $500,000 worth of limestone. Almost one- 
half of the limestone of Indiana and Illinois is used in 
building, nearly all of the output of Pennsylvania is used 
for lime and flux, and all of the output of Maine is 
manufactured into lime. 

The following table shows the rank of the various states 
in the several industries : — 

USES OF LIMESTONE BY STATES, 1889.1 



Uses. 


Penn- 
sylvania. 


Illinois. 


Indiana. 


Mis- 
souri. 


New 
York. 


Ohio. 


Maine. 


Lime 

Building .... 
Street work . . . 

Flux 

Bridges, dams, etc., 


ii. 
$1,195,955 

VIII. 

238,431 

IX. 

72,512 
i. 
949,083 

rv. 
155,653 


VIII. 

$366,245 

i. 
1,084,556 

505,576 

ii. 
166,507 


IX. 

$340,315 

ii. 

994,313 

HI. 

316,722 

XXIII. 

1,056 
i. 

233,710 


VII. 

$465,390 

in. 

542,871 

i. 
670,351 

XVI. 

5,691 
in. 

169,720 


hi. 
$837,613 

rv. 
444,291 

IV. 

197,091 

VII. 

32,750 

ii. 

175,736 


rv. 
$581,325 

v. 
407,388 

v. 
1S3,235 

in. 
105,963 

124,518 


$1,523,499 



Marble. — Vermont is the principal marble-producing 
state of the country, the most important quarries being 
situated near Rutland, where there are extensive beds of 
a well-crystallized white and blue banded, and a clouded 
blue marble associated with a pure white crystalline marble. 
In the West Rutland quarries the strata dip to the west 
from a gentle slope to a dip of nearly 80°; and, in these 
beds, quarries have been opened to a depth of over three 



1 The numerals refer to the relative rank of the various states in the dif- 
ferent branches of the limestone industry. 



BUILDING-STONES AND CEMENTS. 381 

hundred feet. This belt of limestone extends, with greater 
or less continuity, to Long Island Sound, but, in the greater 
part of it, the marble is not suitable for ornamental pur- 
poses ; and, where quarried, is used chiefly as a source for 
lime. 

The so-called marble of Tennessee is not in reality a 
marble, but is a partly metamorphosed limestone in which 
the abundant fossils still show plainly, and by their differ- 
ence of colour and their form, give to much of it its 
particular value. There is a considerable variety of colour, 
from light pink to chocolate brown, and often mixtures 
of these colours. In New York a coarsely crystalline, 
mottled, and banded blue, greenish, and white marble is 
found in St. Lawrence County ; and in Westchester County 
a mottled dolomitic marble is quarried. A dull brown 
limestone, containing fossils, is obtained in Greene County, 
and a black limestone occurs at Glens Falls, in Warren 
County, New York. Georgia, Maryland, California, Penn- 
sylvania, and Virginia are also marble-producers, and in some 
other states this stone has been found. It may be safely 
predicted that the best marbles of the country have not 
yet been exploited ; for, in the Cordilleras, there are exten- 
sive deposits of beautiful and variously coloured marbles, 
which will some day rival the best Italian products. As 
in the case of nearly all building-stones this region, be- 
cause of its inaccessibility, has not been developed ; but even 
at present it would be possible to put upon the market 
some of these beautiful stones. 

In the Eleventh Census report both serpentine and onyx 
are included under marble, and we have no recent statistics 
of the production of these ornamental stones. Onyx is 



382 ECONOMIC GEOLOGY OF THE UNITED STATES. 

found in this country only in the western part. There 
is a deposit of this stone in San Luis Obispo County, Cali- 
fornia, but, although it resembles the Mexican onyx, and is 
very beautiful, it has not as yet assumed marked importance, 
because of its inaccessibility. At present onyx is quarried 
in Arizona, about thirty miles east of Prescott. It outcrops 
here in a bluff, and is stratified with a breccia, being, 
apparently, a precipitation from lime-bearing waters which 
have received their carbonate of lime by percolation through 
the neighbouring igneous rocks. This onyx compares favour- 
ably with that of Mexico, but, although some is sold, our 
chief supply of this stone still comes from the latter country. 

Serpentine is known to exist in various parts of the 
belt of metamorphic rocks, from New England to Georgia, 
and also in the Cordilleran metamorphics ; but it rarely 
occurs in sufficient abundance and of the proper colour 
to be of economic value. There are, however, serpentine 
quarries in Maryland, from which a stone varying in colour 
from pale to dark green is produced. Serpentine is a 
product of metamorphism and alteration from certain rocks 
and minerals, notably from olivine and olivine-bearing 
rocks. 

Over 80 per cent of the marble consumed in this country 
is produced at home, but considerable ornamental stone for 
interior decoration is imported, principally from Carrara in 
Italy, from which place we obtain three-fourths of our 
imports of this stone. Marble is used almost entirely for 
interior decoration, for ornamental work, monuments, grave- 
stones, and some of the more costly buildings. It is not 
nearly so commonly used for building purposes as the other 
stones. 



BUILDING-STONES AND CEMENTS. 



383 



PKODUCTION OF MAEBLE IN THE UNITED STATES. 



States. 


1880. 


1889. 


1891. 


Vermont 


$1,340,000 


$2,169,560 


$2,200,000 


Tennessee 


173,600 


419,467 


400,000 


New York 


224,500 


354,197 


390,000 


Georgia 




196,250 
87,030 


275,000 
100,000 


California 




Maryland 


65,000 


139,816 


100,000 


Pennsylvania 






45,000 


Total for the United States. . 


$2,033,595 


$3,488,170 


$3,610,000 



Summary of Building-Stone Production. 1 — The ten lead- 
ing stone-producing states in 1889 were Pennsylvania, Ohio, 
New York, Maine, Vermont, Massachusetts, Missouri, Illi- 
nois, California, and Connecticut, all of which produced 
more than $2,000,000 worth of stone in the last census 
year. Five other states, Indiana, Colorado, Wisconsin, New 
Jersey, and Minnesota, produced over 81,000,000 worth of 
stone in 1889. Forty-four states and territories produced 
$53,035,620 worth of stone for building and other purposes. 

Of this total, Pennsylvania supplied 13.8 per cent, or 
$7,319,199 worth of stone. All commercial varieties are 
found there, but the chief products are limestone, slate, and 
sandstone. Ohio, which ranks as the second most important 

1 For a more complete statement of the economic importance of the stone 
industry in the various states of the United States, reference may be made to 
the Eleventh Census volume on Mineral Industries, pp. 595-666, and the 
Mineral Besources of the United States, Day (U. S. Geol. Survey) 1889- 
1890, pp. 373-440. An excellent book upon the general subject of building- 
stones is Merrill's Stones for Building and Decoration, New York, 1891. 



384 ECONOMIC GEOLOGY OF THE UNITED STATES. 

stone-producing state, supplies almost exclusively sand- 
stone and limestone, in the former of which it holds first- 
rank. 

All varieties of stone are obtained in the third state, New 
York, but the most important are limestone and bluestone. 
Maine owes its rank to the numerous granite quarries, and 
to the industry of lime production, for which purpose the 
entire output of limestone is employed. In Vermont the 
most important stone is marble, but slate is also quarried 
extensively, and in this industry Vermont holds second 
place, while in the production of marble it has an output 
nearly twice as great as all the other states combined. The 
granite industry, in which Massachusetts holds first rank, is 
the only important stone industry of the state, although 
small quantities of sandstone and limestone are also obtained. 
Missouri produces principally limestone and some granite, 
Illinois practically nothing but limestone, California supplies 
stone of several varieties for local and Pacific Coast con- 
sumers chiefly, and Connecticut is a producer of granite 
and sandstone. Indiana leads in the production of lime- 
stone, and this makes the greater part of its stone output ; 
Colorado produces principally sandstone ; Wisconsin chiefly 
limestone ; New Jersey, sandstone, slate, granite, and lime- 
stone ; and Minnesota, limestone and sandstone. 

It will be noticed that the metamorphic rocks, slates, and 
marbles, and the granites, occur almost exclusively in the 
belt of metamorphic rocks extending from Canada to 
Georgia and in the area of metamorphics about Lake Supe- 
rior. Other metamorphic areas, particularly in the Cordil- 
leras, contain stores of these stones, but they will not be 
extensively quarried, except for local purposes, for the reason 



BUILDING-STONES AND CEMENTS. 385 

that they cannot compete with the eastern stone found near 
the market. 

The sedimentary rocks, limestones, bluestones, and sand- 
stones, are obtained principally from the Central States, 
where the strata are all of Palaeozoic age and nearly hor- 
izontal. Being horizontal, they are not too much altered 
or broken, and yet, on account of their great age, they are 
sufficiently cemented and indurated for building purposes. 
Not a small percentage of these stones comes from the 
strata of the same age, which are folded into the Appa- 
lachians; and by far the greater part of the Cordilleras 
are made up of similar sedimentary rocks, which, for the 
same reason that applies to the metamorphic and igneous 
building-stones, are not of value except for local purposes. 

There is no need of importing any kind of building-stone, 
and, if called upon, we could quarry enough of nearly 
all kinds of stone to supply the needs of the world. No 
other nation has an output of building-stone so varied and 
so great as that of the United States, and no other nation 
has such immense stores which are of good quality, but of 
no immediate value because of the absence of a market. As 
has been said above, a building-stone to be of value in this 
country must be either of exceptional quality or accessible 
to a good market. 

The following table shows the output of all kinds of stone 
from the fifteen most important states, each of which pro- 
duces over 11,000,000 worth a year. In 1889 the production 
of these states was within $10,000,000 of the total for the 
country. 



386 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



PRODUCTION OF STONE IN THE UNITED STATES, 1889. 

Pennsylvania $ 7, 319, 199 

Ohio 4,561,590 

New York 4,418,143 

Maine. . . 3,968,838 

Vermont 3,789,709 

Massachusetts 3,307,578 

Missouri . 2,516,159 

Illinois 2,208,503 

California 2,126,515 

Connecticut 2,112,960 

Indiana 1,933,319 

Colorado 1,676,862 

Wisconsin 1,264,016 

New Jersey 1,172,119 

Minnesota 1,102,008 

Total for the United States . . . $53,035,620 
BUILDING-STONE PRODUCTION OF THE UNITED STATES. 



Kinds. 


1880. 


1889. 


1891. 


Limestone 


$6,856,681 


$19,095,179 


$15,762,000 


Granite 


5,188,998 


14,464,095 


13,867,000 


Sandstone 


4,780,391 


10,816,057 


8,700,000 


Slate 


1,529,985 


3,482,513 


3,825,746 


Marble 


2,033,595 


3,488,170 


3,610,000 


Bluestone 




1,689,606 


.... 


Total building-stones and lime 


$18,356,055 


$53,035,620 


$47,294,746 



BUILDING-STONES AND CEMENTS. 387 

Natural and Artificial Cements. 1 
By mixing burned limestone or lime with sand and water, 
a plaster is produced, which, upon drying, hardens to form 
a cement, the ordinary material used for plaster ; and the 
importance of this industry may be inferred from the fact 
that, in 1892, 70,000,000 barrels (200 lbs. each), valued at 
$38,500,000, were produced in this country. Cements which 
have the power of setting and hardening under water are 
commonly called hydraulic and Portland cements. These are 
either a natural or artificial mixture of carbonate of lime and 
clay heated to a high temperature and then ground to a powder. 
Argillaceous limestones sometimes contain the proper pro- 
portion of clay and carbonate of lime for the formation of 
hydraulic cement; but more commonly the per cent of these 
materials is not exactly correct, and then either a poor cement 
or a valueless product results. Properly speaking, hydraulic 
cement is made from natural hydraulic limestones, burned at 
a moderate temperature, while Portland cement is made 
from a mixture of chalk, or marl, and clay burned at a high 
heat. In this country hydraulic cement is made chiefly in 
New York state, from a shaly limestone, which occurs at the 
top of the Salina group, and extends through several counties. 
The industry is principally concentrated in Ulster County. 

Portland cement, which sets more slowly, but produces 
a much harder and stronger cement, is manufactured in 
England, Germany, and France on a very large scale; but 

1 This industry depends so largely upon the method of manufacture, that 
little is necessary here, excepting to point out the source of the materials 
used. Valuable accounts of the cement industry will be found in The 
Mineral Mesources of the United States, Day (U. S. Geol. Survey), 1891, 
pp. 529-538, and in Rothwell's Mineral Industry, 1892, pp. 49-56. 



388 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



in this country very little is produced, although calcareous 
marls and chalks suitable for its manufacture are found in 
numerous places, and the industry promises to grow rapidly. 
Great care is needed in obtaining the proper proportion of 
clay and carbonate of lime, and also in mixing these together. 
The following analyses will give an idea of the chemical 
character of the cement-rocks and cement : — 



ANALYSIS OF HYDRAULIC CEMENT ROCK, ROSENDALE, 
ULSTER COUNTY, NEW" YORK. 

Carbonate of lime 45.91 

Carbonate of magnesia 26.14 

Silica and insoluble 15.37 

Sesquioxide of iron, and alumina .... 11.38 

Water and undetermined compounds . . 1.20 

There is, however, great variability in composition, but 
the above is a fair average analysis. 

ANALYSES OF PORTLAND CEMENT MIXTURES. 





Coplay (Pa.) 

Natural Eock and 

Limestone. 


Wagner' s 

(N.T.) 

Clay and Marl. 


Yankton 

(South Dakota) 

Clay and Limestone. 




Argillaceous 
Limestone. 


Limestone. 


Clay. 


Marl. 


Clay. 


Limestone. 


Lime 


37.60 


50.15 


11.25 


51.55 


5.28 


51.00 


Silica 


18.34 


4.46 


44.74 


1.06 


61.53 


4.14 


Alumina 


4.08 


1.00 


18.70 


.64 


20.74 


1.81 


Sesquioxide of iron . . . 


3.41 


.48 


4.25 


.35 


4.01 


2.72 


Magnesia 


1.39 


.87 


1.29 


.91 


1.72 


Trace 


Alkalies 


.19 


Trace 


1.20 




2.29 


Trace 


Carbonic acid 


31.05 


40.40 


7.50 


40.70 


3.09 


39.99 


Sulphuric acid 






2.78 


2.07 






Sulphur 


.73 


.15 






1.26 


.50 


Water 






9.25 








Organic and undetermined, 


3.21 


2.49 




2.86 


.08 




Total 


100.00 


100.00 


100.96 


100.14 


100.00 


100.16 



BUILDING-STONES AND CEMENTS. 



389 



There is, therefore, a marked variability in the kind and 
composition of the rock used in the manufacture of these 
artificial cements. A greater uniformity is obtained in the 
products, but even here there is some variety. 

ANALYSES OF NATURAL AND PORTLAND CEMENTS. 



Silica . . 

Alumina ) 

Sesquioxide of iron . . . ) 

Lime 

Magnesia ....... 

Alkalies 

Carbonic acid 

Undetermined 



Hydraulic. 



Rosendale, 

Ulster Co., 

N.Y. 



22.75 

16.70 

37.60 
16.65 

5.00 
1.30 



Akron, 
N.Y. 



29.64 

6.42 

54.77 
9.17 



Portland. 



Coplay, 
Pa. 



20.64 

6.93 

5.41 

62.79 

1.72 

.27 

.99 

1.14 



Onondaga 
Co., 

N.Y. 



22.10 

6.84 

2.10 

63.00 

.97 

4.00 

.90 

.09 



PRODUCTION OF CEMENT IN THE UNITED STATES. 





Hydraulic. 


Portland. 


Total 




Barrels. 


Value. 


Barrels. 


Value. 


Value. 


1882 .... 
1885 .... 
1892 .... 


3,165,000 
4,000,000 
8,132,593 


$3,481,500 
3,200,000 
5,549,163 


85,000 
150,000 
525,360 


$191,250 

292,500 

1,036,935 


$3,672,750 
3,492,500 
6,586,098 



In 1891 the total value of the hydraulic cement output was 
$5,613,522, of which New York produced 13,046,279, Indiana- 



390 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Kentucky 1983,456, and Pennsylvania $536,600. Of the 
total of $1,067,429 worth of Portland cement produced 
in this country in 1891, Pennsylvania supplied $532,850, 
and New York $290,250. Our imports of cement in 1892 
amounted to $3,378,824, this being principally Portland 
cement. 



CHAPTER XVII. 

SOILS, CLAYS, FERTILIZERS, ARTESIAN WELLS, AND 
MINERAL WATERS. 

Soils. 1 

The subject of soils cannot be treated here in more than 
a very general and cursory manner, and the chemical con- 
sideration must be entirely omitted. In general, soils may 
be classified into two groups, — indigenous and transported. 
The first group includes those which have been formed 
approximately at the point where they rest, the second those 
which have been borne from some outside source. Of these 
there are several kinds. 

Residual soils may be classed as indigenous, and they 
result from the decay and disintegration of the rock which 
underlies them. A rock, even the hardest and most dura- 
ble, is susceptible to changes in structure -x>r even in chem- 
ical composition under the ordinary influences of weather. 
The building of sandstone, limestone, or granite shows 
the effect of weathering by a crumbling which results from 
long-continued exposure. The rain dissolves soluble por- 
tions and forms crevices into which water may enter, and 
this, if frozen, prys open the crevices and aids in the disin- 
tegration. Sudden changes of temperature from warm to 

1 Professor N. S. Shaler has prepared an admirable treatise upon soils, 
which is published in the Twelfth Annual Report of the U. S. Geol. Survey, 
pp. 213-345. 

391 



392 ECONOMIC GEOLOGY OF THE UNITED STATES. 

cold, or from cold to warm, cause contraction or expansion, 
which aids the fragments in breaking. Lichens clinging to 
the wall send root-like threads into the crevices, and these, 
upon the growth of the plant, tend to wedge fragments from 
the rocks. 

It is exactly this process which causes the formation of 
residual soils. The rock disintegrates, percolating water 
permeates the resulting material, and, dissolving the soluble 
minerals, carries them away in solution. The work which 
lichens at first did on a small scale, is continued on a larger 
scale by the prying action of the roots of larger plants and 
trees. The ants, the rodents, the earthworms, and the many 
creatures which live in the soil aid in the work. As a result 
of these various agents, rock crumbles and tends to become 
ever finer in texture, while at the same time the soluble salts 
are removed. There is a tendency, therefore, to concentrate 
the insoluble particles and thus form a residue, — the normal 
residual soil. 

By the decay of rocks, the soil at first maintains certain 
characteristics of the parent rock, and a limestone soil there- 
fore differs from a granite soil. In other words, certain of 
the soluble salts are not removed, and these give to the 
resulting product a character indicative of its origin. Ulti- 
mately, however, all of the soluble salts would be removed, 
and the resulting soil would not vary essentially from one 
rock to another. It would be composed of the nearly insol- 
uble silica, kaolin, and other similar products/ whether the 
source were limestone or granite. 

In the rocks — in granite, for instance — there are minerals 
which by their decay form salts of potassium, sodium, cal- 
cium, etc., which are valuable as plant food, and it is these 



SOILS, CLAYS, FERTILIZERS, ETC. 393 

which the plants absorb from the soil. On the other hand, 
there are contained in many rocks organic remains, either 
animal or plant, — as, for instance, the organic contributions 
forming limestone, — and these are especially rich in plant 
food. Indeed, during the formation of a soil, organisms, par- 
ticularly plants, at their death, enrich the soil which has 
supported them, by returning to it a portion of that which 
they have extracted from the air and the soil. The decaying 
vegetation forms a loam, particularly in swampy places, 
where it is protected from decay and entire dissipation, and 
the influence of this is felt to a distance of several feet 
below the surface. 

At times the conditions favour the formation of an organic 
soil. This is particularly noticeable in swampy regions, 
where vegetable growth is rapid and decay slow. Deep 
loams and peat bogs result, and these, when properly drained, 
make valuable soils. 

In the ocean, material is deposited sometimes in the form 
of organic remains, sometimes as inorganic sediments. 
When these are raised above the sea, they may be in one of 
two conditions, — either consolidated or loose and unconsoli- 
dated. If the former, they must be disintegrated before 
forming soils ; but if in the latter condition, they are 
suited to the growth of plant life as soon as drained. It 
becomes a question whether the latter are to be considered 
indigenous or transported, soils ; but, since there is every 
gradation from these to the typical transported soil, and, on 
the other hand, between the unconsolidated and consolidated 
rocks, they may be considered to be intermediate in position. 
Material is prepared upon the land by disintegration, and 
transported seawards, where it is assorted and deposited; 



394 ECONOMIC GEOLOGY OF THE UNITED STATES. 

and upon the elevation of that part of the sea-bottom it 
may again begin the cycle. 

Instances of such soils are found in the coastal plains 
extending from New Jersey to the Rio Grande, but most 
of these are still too swampy to be of use to man. Of 
the organic indigenous soils, the swamp lands of Florida, 
the Dismal Swamp, and the innumerable morasses and bogs 
of the northeastern states are illustrations. A residual soil 
covers the greater part of the area of the United States 
south of the glacial belt, and throughout this area the char- 
acter of the soil is distinctly influenced by the underlying 
rocks. This soil varies in thickness up to many feet, and in 
some tropical regions, such as Brazil, this residual soil has a 
thickness of several scores of feet. 

Excepting on a plain, it is not strictly accurate to speak of 
an indigenous soil. Upon hillsides the action of gravity 
tends to cause the soil to creep slowly down toward the 
valley, and even upon moderate slopes this creeping action 
is noticeable. In arid lands the peculiarities of the climate 
make this more noticeable. Heavy rainfalls occur at rare 
intervals, and the tendency is to cause a wash of the disinte- 
grated materials from the base of the mountains out upon 
the plateau. Gravel slopes are thus formed, as the result of 
the action of gravity, aided by the wash of the heavy rains. 

From these types of partly moved soils, there is every gra- 
dation to the talus soil which forms at the base of a cliff by 
the constant dropping and subsequent disintegration of rock 
fragments. Eventually the talus is built up to a point where 
its slope meets the top of the cliff, or a point where the talus 
slope is continued in the hill. In other words, the hill wears 
back by weathering ; and this weathered slope and the talus 



SOILS, CLAYS, FERTILIZERS, ETC. 395 

slope become continuous. If, however, a stream flows at the 
base of the cliff, and removes the talus, the above condition 
may for a long time be delayed. The talus soil resembles 
the indigenous soil in the fact that it has a character resem- 
bling that of the rock of the cliff, and that it is derived by 
disintegration. But, on the other hand, it has been removed 
for some distance, and is very liable to be a commingled 
product derived from the several kinds of rocks which form 
the cliff. These soils are very common in the Cordilleras 
at isolated points. 

In their passage to the sea, streams take such fragments 
as they find within their grasp, and transport them down 
stream, always tending to divide them into smaller frag- 
ments. In the course of their development, streams build 
flood plains, and often terraces and deltas, by reason of cer- 
tain causes which cannot be explained here. These, which 
are usually excellent soils, are generally fine-grained in tex- 
ture, and are composed of materials from all parts of the 
drainage area above the point of deposit. The Mississippi 
valley furnishes the best illustration of this class of soils, but 
in a minor way all the smaller rivers are likewise flood- 
plained. Akin to these soils are the sea-bottom sediments 
which are raised above the sea, and the lake-bottom deposits 
which result from the filling and drainage of lacustrine bodies. 

Another group of transported soils, although of very little 
importance, is that of aerial or seolian soils. Even in moist 
climates, there are times when the dust blows about, and this 
aids, not only in transportation, but also in the disintegration 
of rock fragments. In the arid lands this blowing about 
of sand and dust becomes of much more importance, and all 
the soils there are in a measure transported by this means. 



396 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Locally, in these regions, where the conditions are favourable, 
and also along lake and sea shores, blown sands form extensive 
tracts of sand-dunes which are typical seolian soils, usually 
barren of vegetation, not alone because of the fact of their 
constant movement, but also because they are actually barren 
of plant food. Usually quartz and sand grains predominate, 
and these form a porous deposit, through which the water 
passes freely without causing a decay of the minerals and 
the formation of plant food. Only hardy and sand-loving 
plants are able to obtain a footing there ; but if these succeed 
in growing in sufficient abundance to prevent the movement 
of the sand, they soon bring about the disintegration of the 
grains and the formation of a soil capable of sustaining other 
forms of vegetation. 

A final important group is that of glacially formed soils. 
In certain mountains snow accumulates, and, moving down 
the valleys, forms a glacier which ploughs against the 
valley bottom and sides, rasping and grinding off fragments 
as it moves, and transporting these to its terminus, together 
with the fragments which fall upon it from the overhanging 
cliffs. Thus, at any given time, there is beneath a glacier 
a deposit consisting of large boulders and finer fragments, 
even fine-grained clay, all mixed intimately. If the glacier 
should disappear, the valley bottom would be covered with 
this material, forming a glacially transported soil. At the 
terminus of the glacier, moraines are formed of the material 
brought by the ice, and left when it was able to move no 
farther. From beneath the ice, streams issue ; and these 
assort the materials, leaving the large boulders behind, car- 
rying the fine clay some distance from the glacier, and 
depositing sand plains and terraces between these two points. 



SOILS, CLAYS, FERTILIZERS, ETC. 397 

Almost exactly this same condition has been experienced 
by the northern sections of this country, north of a line ex- 
tending approximately from Nantucket, through Long Island, 
central New Jersey, northwestern Pennsylvania, Cincinnati, 
Ohio, Wisconsin, and thence northwestward to Dakota. 
Nearly all of this region was beneath an ice-sheet resembling 
that of Greenland. Any soil which may have existed before 
the oncoming of the glacial period was swept away ; and 
when finally the ice melted, the surface was littered with a 
glacially transported soil, in some places morainal, in some 
the general sheet of unstratified till or ground moraine, and 
elsewhere^ with sand plains and terraces. 

In a limestone region the soil contains not only fragments 
of this material, but of many rocks derived from more north- 
ern regions. Where the motion of the ice was for a long 
distance over a limestone belt, as in some of the north and 
south valleys of New England and New Jersey, the influ- 
ence of the limestone is markedly noticeable in the soil. 
But it is not uncommon to find, over a given stratum, a soil 
almost free from this material. 

In places the deposit is thick, again it is thin, and, 
over large areas, no glacial soil was left. The time since 
the close of the glacial epoch is so short that in such 
places residual soils have not been formed, and the bare 
rock outcrops. Where the country rock is hard, well jointed, 
and not easily disintegrated, as in the granite and gneiss 
regions of New England, the proportion of boulders in 
the soil is very great, and agriculture is carried on with 
difficulty. Thus there is a marked difference in the charac- 
ter of the soil north and south of the terminal moraine. 

In soils of all these characters plants of various kinds 



398 ECONOMIC GEOLOGY OF THE UNITED STATES. 

grow. Some are well adapted to nearly all varieties of 
plants, others support only certain kinds. In a state of 
nature the plants rob the soil of certain elements, but they 
return to it not only a part of that which they extracted, 
but also some of the carbon which they have absorbed from 
the air. Moreover, they furnish a vegetable coating, which 
protects the soil from being washed away, and furnishes 
water percolating through it with certain acids which dis- 
integrate the particles of rock. It also delays the passage 
of this percolating water so that it does not sink readily 
into the soil and wash away the plant food. 

Man has come into the field with his modern methods 
and implements, and has begun to rob the soil of its natural 
stores of plant food. Extravagant and even foolish methods 
have been introduced, and, in this country in particular, 
thoroughly prodigal methods have been adopted. The 
abundance of land, its virgin richness, and the fact that 
we have not had centuries of experience in tillage, have 
tended to make us thoughtless of our duty to the soil 
and our descendants. The wealth of the nation is largely 
dependent upon the tillage of the soil, and methods which 
will ultimately prove disastrous should be avoided. Already 
in the older settled districts the soil is impoverished, and 
the time is not far distant when our western farm lands 
will need to be treated scientifically or be abandoned. At 
present the average farmer is taking from the soil all it 
will yield and returning nothing to it. Moreover, he is 
interfering with the natural formation of plant food by 
the removal of the loam, and by rendering the soil porous 
by ploughing so that water passes through it as it does 
through a sand-dune. He should return that part of the 



SOILS, CLAYS, FERTILIZERS, ETC. 399 

vegetation which he does not use, and indeed he must do 
more. The peat beds, swamp loam, manure, marls, guanos, 
and phosphates must be more commonly used. 

Clays. 1 

An almost infinite variety of clay occurs in this country, 
and its abundance is so great that for ordinary purposes 
it is readily accessible. There are numerous ways in which 
it is derived, the most common being as a result of rock 
decay. Beds of clay are found throughout the sedimentary 
strata, either still incoherent, or consolidated, and sometimes 
even transformed to slate. These are chiefly formed as 
sediments, by the deposition of the fine-grained products 
of rock decay. Ordinarily these are too impure for any 
but the roughest uses, and some of them cannot be used 
at all. For some purposes, such as the manufacture of 
white pottery, pure kaolin is needed, but for tiling and 
bricks, impure clays may be used. 

The first stage in the formation of much of the clay 
is the decomposition of the rock, a process which is every- 
where in progress. The mineral which is of most impor- 
tance in the production of the finer grades of clay is 
feldspar, which, by its decay, loses the sodium, potassium, 
and other soluble salts, while, as an ultimate product, kaolin, 
or hydrous silicate of alumina, remains. Such clays in 
place are very rare, for they are usually mixed with impuri- 
ties of one kind and another; but in many cases, for the 
better class of porcelain and other ware, rocks which are 

1 The subject of clays is admirably treated by Professor R. T. Hill in the 
Mineral Besources of the United States for 1891, pp. 474-528. 



400 ECONOMIC GEOLOGY OF THE UNITED STATES. 

disintegrating, and, in some cases, pure feldspar, are crushed 
and washed to remove the impurities. 

More commonly workable clays occur in beds where they 
have been deposited by sea or lake, in some cases in the 
form of nearly pure kaolin, but more commonly as impure 
clays, varying greatly in composition, texture, and colour. 
From these, bricks, drain tiles, chinaware, furnace linings, 
pottery, various utensils and ornamental pottery, etc., are 
manufactured by the aid of heat and partial melting. 
Not a little clay is used for purposes of adulteration and 
as a filling for cheap grades of paper. 

For these several purposes different kinds are needed, 
and consequently different industries spring up in various 
localities. Clays known as fire-clays are suited to with- 
stand high temperatures by reason of the absence of 
alkaline material. These are particularly abundant in 
the Carboniferous rocks associated with coal beds, the 
plants having been instrumental in the withdrawal of 
the alkalies. Brick clays must be made of a natural or arti- 
ficial mixture of sand and clay. When a red colour is 
needed, iron salts must also be present. Certain alkalies 
are also needful to aid in the partial fusion of the clay 
when heated. 

Some brick clays are the result of residual decay; some 
are worked-over products of disintegration deposited in 
water, and in this country a large proportion of these clays 
are directly or indirectly the result of glacial action. As 
the ice moved over the rocks, they were ground and rasped 
until a rock flour was produced which was sometimes depos- 
ited in marginal lakes, or in the river-terrace plains near 
the ice front, and sometimes deposited directly from the 



SOILS, CLAYS, FERTILIZERS, ETC. 401 

ice when it melted. The distribution of these clays in the 
glacial belt is very widespread, and every state and nearly 
every district has such clays for the manufacture of brick 
for local demands. Certain large centres which produce 
brick of an exceptional quality ship some of their output 
to a considerable distance ; but most of the producers sup- 
ply only local markets. This is less true of the other clay 
industries, excepting those producing the coarsest products ; 
and very fine ornamental ware is sent from one country 
to another. 

Clays are of all ages from the Cambrian to the present, 
but in this country the most important are of Cretaceous, 
Tertiary, and Quaternary age. The brick clays are chiefly 
of Quaternary age, being either recently deposited in river 
valleys, or of glacial origin. Fire-clay occurs abundantly 
in the Carboniferous, and some in this country occur else- 
where in the Palaeozoic. In addition to actual clays, flint, 
quartz, and feldspar are ground up and used as clay. There 
are large quantities of these minerals, as well as of clay, 
which are not at present utilized. 

Notwithstanding the great importance of the industry of 
brick production, there are no statistics available. In 1891 
the value of the potter's materials, including kaolin, fire- 
clay, ground flint, and feldspar, was over $1,000,000. New 
Jersey is the most important state in this respect, but many 
others have valuable pottery industries. Probably the brick 
industry is many times more valuable than that of the man- 
ufacture of pottery. 

The industry of feldspar production for grinding and 
mixing with clay and for a glaze is centred in Maine, 
Connecticut, New York, and Pennsylvania. The annual 



402 ECONOMIC GEOLOGY OF THE UNITED STATES. 

product varies from 8000 to 15,000 long tons, valued at 
about $5 a ton, and this comes from coarse granitic or peg- 
matite veins. Flint occurs in bands and nodules of con- 
cretionary origin in limestones and chalk. It is an impure 
form of silica, and is used extensively in the manufacture 
of pottery. There are vast quantities in the west and 
southwest which are not at present utilized. In 1891, 
15,000 long tons, valued at $60,000, were produced in the 
United States. 

Fertilizers. 

General Statement. — Various substances are used for the 
purpose of returning to the soil the elements needed in plant 
growth, thereby enriching impoverished soils. Manure and 
other waste products of organic origin are commonly used 
for this purpose, and there are extensive establishments for 
the manufacture of artificial guano from the remnants of 
fish and other animals, obtained during the process of prep- 
aration for the market. Vegetable products are also made 
to give up their plant food to the soil. Sometimes the 
plants which have grown upon the field are allowed to 
decay there, and at times loam and peat are added to the 
soil. These products do not come within the scope of this 
work, and none of them, with the exception of artificial 
guano, are of more than local importance. There are, 
however, several classes of important economic products 
which are of use for returning to the soil needful sub- 
stances which have been extracted by plants. These are 
limestone, marl, gypsum, and the various phosphates. 

Limestone and Marl. — It is a well-recognized fact that 
limestone soils are rich in plant food, and consequently the 



SOILS, CLAYS, FERTILIZERS, ETC. 403 

addition of this rock to a poor soil is of value. This is 
due partly to the presence of the carbonate of lime, and 
partly to other substances of organic origin furnished the 
limestone by the animals which formed it. For the pur- 
pose of a fertilizer, limestone is burned to form lime, and 
then spread upon the soil. A portion of the lime product 
mentioned in the preceding chapter is used for this pur- 
pose, while many farmers burn limestone for their own or 
for local use in regions where it can be easily obtained. 
There are no statistics for the production of lime for fertil- 
izing purposes. 

Marl is a calcareous clay, owing its calcareous nature to 
the presence of numerous shells of mollusca. Being a soft 
clay, it is easily obtained; and before the introduction of 
cheap phosphatic fertilizers, it was extensively used for fer- 
tilizing purposes, particularly in New Jersey, where it is found 
most abundantly. This substance occurs locally in many 
places, in the bottom of swamps, and it should be of more local 
importance than it is. In the coastal plains of Cretaceous 
and Tertiary age there are extensive deposits of marl and 
greensand ; and since these are at present used only for local 
purposes, statistics of their production are difficult to obtain. 
During the census year 1880 the value of the marl product 
was approximately 1500,000, and in 1891 only $67,500, this 
representing 135,000 tons of marl. This calcareous clay is 
also of value in the manufacture of Portland cement. 

Gypsum. — This mineral, the sulphate of lime, is used for 
two purposes principally, — one as "land plaster" for a 
fertilizer, the other, and the most important, calcined, to 
form plaster of Paris. Gypsum occurs in all rocks, in 
minute quantities ; but in many sedimentary strata, it is suffi- 



404 ECONOMIC GEOLOGY OF THE UNITED STATES. 

ciently abundant to give to water percolating through them 
a certain peculiarity known as "hardness." The water of 
nearly all rivers and lakes, and of all oceans, carries it in 
solution; and when lakes fail to overflow, and are trans- 
formed to dead seas, this mineral becomes concentrated, and 
may finally be precipitated in beds. Much of the supply 
obtained in this country is associated with salt, and has prob- 
ably originated in this way. In the Cordilleras there are 
large areas of gypsum, called white sands, in the dried-up 
beds of extinct lakes ; but this is at present of no value 
except for local purposes. 

There is still another way in which this mineral may be 
formed in the rocks, and some believe that many of the gyp- 
sum beds are of this origin. This is by the alteration of 
beds of limestone, through which sulphurous waters are per- 
colating. It is doubtful how far this can be extended to 
account for the commercial deposits of gypsnm, but some of 
this mineral is undoubtedly formed in that way. Sulphurous 
waters are not uncommon, the sulphur being furnished by 
decaying organic remains or by iron pyrites ; and these, 
coming in contact with limestone beds, may very readily 
alter them to the sulphate of lime. 

The association of gypsum with salt, however, indicates 
that much of it is the result of precipitation from salt 
lakes ; and for the western deposits this is unquestionably 
the true explanation. In different parts of the world, 
different ages have had prevailing conditions of aridity, 
attended by the formation of dead seas ; but in this coun- 
try the Permian, Tertiary, and Quaternary have been the 
most important periods in which arid conditions have pre- 
vailed. This applies to the western part of the country ; and 



SOILS, CLAYS, FERTILIZERS, ETC. 



405 



there is some reason to believe that, during the Palaeozoic, 
there were periods of aridity in the east. 

PRODUCTION OF GYPSUM IN THE UNITED STATES, 1891. 



States. 


Calcined 

for 
Plaster. 


Fertil- 
izer. 


Sold 
Crude. 


Total 

Product. 

Short Tons 

(2000 Lbs.). 


Total 
Value. 


Michigan 

Kansas 

New York .... 

Iowa 

Virginia 

South Dakota . . . 
California, Ohio, Utah, ) 
and Wyoming . . / 


$173,175 
159,832 

53,250 

4,938 
90,810 


$28,550 

210 

53,513 

4,845 

22,222 
4,680 

3,336 


$22,000 
1,280 
5,058 

352 


79,700 
40,217 
30,135 
31,385 
5,959 
3,615 

17,115 


$223,725 

161,322 

58,571 

58,095 

22,574 

9,618 

94,146 


Total 


$482,005 


$117,356 


$28,690 


208,126 


$628,051 



GYPSUM PRODUCTION OF THE UNITED STATES. 

1880 $400,000 

1885 405,000 

1890 428,625 

1892 675,000 

In 1891 we imported 1226,319 worth of gypsum. 

Phosphatic Fertilizers. 1 — Mineral Phosphate. The phosphatic 
fertilizers may be divided into mineral phosphates, of which 
apatite is the only representative, and rock phosphates which 
consist of guano, bone beds, and phosphatic nodules. Mineral 
phosphate, or apatite, the phosphate of lime, occurs in nearly 

1 A valuable treatise on The Nature and Origin of Phosphate of Lime, 
by R. A. F. Penrose, Jr., forms Bull. 46, U. S. Geol. Survey. 



406 ECONOMIC GEOLOGY OF THE UNITED STATES. 

all eruptive and metamorphic rocks, generally in small 
grains and crystals, and in such small quantities that it 
does not sensibly increase the value of the enclosing rock 
as a soil-producer. In some rocks, principally in the meta- 
morphic limestones associated with the Archean, apatite is 
often more abundant, and seems here to be the result of 
segregation into crystal form of the phosphatic substances 
originally disseminated through the limestone in the form of 
organic remains. The bones of vertebrates, the flesh of many 
animals, and, in some cases, the tests or shells of animals, par- 
ticularly certain Crustacea, contain some phosphate of lime ; 
and as a result of this, certain limestones are sufficiently 
phosphatic to make high-grade soils. But there is no reason 
for believing that the apatite which occurs in igneous and 
metamorphic rocks is of organic origin ; but, on the contrary, 
this is probably the original source of the organic phosphatic 
materials extracted by the intervention of organisms. 

Apatite is not mined in this country ; but in Canada large 
quantities of it occur in veins in the Laurentian limestones 
and gneisses, near Ottawa, Perth, and Kingston. Here it is 
mined, separated by hand, and crushed, chiefly by the farmers 
who own the land and by small companies. A great decline 
in this industry has been caused by the competition of the 
South Carolina and Florida phosphates. 

Guano. — This is the excrement of birds, such as divers 
and penguins, which resort in great numbers to some of the 
islands off the west coast of South America. It is found 
elsewhere, but the climatic conditions have not favoured its 
accumulation into extensive deposits. In 1804 Humboldt first 
called attention to the deposits of guano on the Chincha 
Islands, off the coast of Peru; and from 1842 to 1873, when 



SOILS, CLAYS, FERTILIZERS, ETC. 407 

they were exhausted, nearly 14,000,000 tons, valued at from 
$45 to $70 a ton, were exported from there. Since then 
other islands have been producing guano ; and although the 
older deposits are approaching exhaustion, the province of 
Tarapaca and the off-lying islands are still exporting this 
substance. In 1879 Chili seized these deposits, and still 
controls them. Chili exported, in 1890, 41,323 metric tons 
of guano, valued at $1,237,003; but the time is not far distant 
when these islands will cease to produce guano. Smaller quan- 
tities are obtained in the Argentine Republic and Uruguay. 

Bock Phosphates. — In this country the most important 
fertilizer is the rock phosphate, which exists in the form of 
bone beds and phosphatic nodules of concretionary origin, 
usually occurring together; and the recent discoveries of 
these substances have given to this country the leading rank 
in the production of natural fertilizers. South Carolina and 
Florida are the important phosphate-producing states, but 
deposits also exist in North Carolina, Alabama, and other 
southern coastal states. These deposits consist of a white 
phosphatic limestone or a limy marl-like clay containing layers 
and nodules of more pure phosphate of lime and bones and 
teeth of mastodons, sharks, and other land and marine animals. 

The South Carolina deposits were recognized in 1797; 
but it was not until 1867 that their true value was known, 
and since then the production of phosphates in this state 
has rapidly increased. There are two methods of mining 
these deposits : one dredging in the river beds, the other 
removing the "land rock" by means of open trenches. 
The phosphate is then crushed, washed, dried in kilns, and 
finally converted into superphosphates. Beaufort is the 
principal locality, and here, as well as elsewhere, there is a 



408 ECONOMIC GEOLOGY OF THE UNITED STATES. 

wide variation in the character, composition, and distribution 
of the phosphates ; but they are all distinctly bedded with 
the other strata of Tertiary age. 

The following table shows the increase in output of phos- 
phate rock in South Carolina, a marked decrease being 
noticed since 1889, when the Florida phosphates became of 
importance. In 1890, 212,102 tons were obtained from the 
rivers by dredging, and the balance of the 537,149 tons from 
the land rock. 

PRODUCTION OF PHOSPHATE ROCK IN SOUTH CAROLINA. 
Long Tons (2240 Lbs.). 

1867 6 

1868 12,262 

1870 65,241 

1875 122,790 

1880 190,763 

1885 395,403 

1889 548,585 

1890 537,149 

1891 475,506 

1892 350,000 

Deposits of phosphate of lime were discovered in Florida 
in 1883, but not until 1888 were they known to exist in 
large quantities. In this year a fossil tooth was found in a 
white subsoil, and the latter upon analysis was found to be 
an important phosphate rock. Great excitement and active 
exploration followed, and extensive developments have been 
made which prove that this area is the largest and most im- 
portant phosphate region in the country. The phosphate is 
in the form of (1) layers and nodules, called respectively 
" hard rock" and "land pebble"; (2) less pure phosphatic 
limestone, filling the spaces between the nodules and layers, 
called "soft rock"; (3) vertebrate fossils; and (4) "river 



SOILS, CLAYS, FERTILIZERS, ETC. 



409 



pebbles," which are derived from the land deposits washed 
down and accumulated by the streams. The following table 
shows the remarkably rapid development of the phosphate 
production of Florida : — 

PHOSPHATE PRODUCTION OF FLORIDA. 
Product. 
Year - Long Tons (2240 Lbs.). VaLUE ' 

1888 3,000 $25,000 

1889 4,100 32,800 

1890 46,501 338,190 

1891 112,482 703,013 

1892 262,382 

The following table of analyses shows the composition of 
these phosphates : — 

ANALYSES OF SOUTH CAROLINA AND FLORIDA 
PHOSPHATE ROCK. 



Phosphoric acid (P 2 5 ) 

Lime(CaO) . . . . 

Alumina (A1 2 3 ) . . . 

Ferric oxide (Fe 2 3 ) . 

Magnesia (MgO) . . 

Alkalies (Na-jO) . . . 

Sulphuric acid (S0 3 ) . 

Fluorine (Fl) . . . . 

Chlorine (CI) . . . . 

Silica (Si0 2 ) . . . . 
Carbonic acid (C0 2 ) 

Insoluble matter . . . 

Moisture 



luraville, 
Florida. 


South Carolina. 


33.91 


26.0 to 29.0 


47.02 


35.0 to 42.0 


2.37 


Traces to 2.0 


1.46 


1.0 to 3.0 


0.39 


Traces to 2.0 


0.19 




0.36 


0.5 to 2.0 


2.35 


1.0 to 2.0 


0.08 




0.10 


4.0 to 12.0 


2.67 


2.5 to 5.0 


5.07 


2.0 to 6.0 l 


3.96 


0.5 to 4.0 



1 Organic matter and combined water. 



410 ECONOMIC GEOLOGY OF THE UNITED STATES. 

The price of phosphate rock varies greatly according to 
the proportion of phosphate of lime, but in 1891 it averaged 
about |6.25 a ton. No doubt these deposits will in time be 
exhausted, but there are still immense stores in sight and 
enough to last for long periods of time. France, Belgium, 
and some other countries, contain phosphate beds of similar 
character and origin. 

The origin of these deposits is from organic remains, as is 
indicated by the presence of bones of vertebrates. For some 
reason both land and marine vertebrates resorted to the estu- 
aries and bays, and their remains became commingled. In 
Florida, at the time of formation of the phosphate beds, there 
existed above the sea a series of small keys and islets bathed 
by the warm southern currents ; and in the straits between 
them marine life abounded, while upon the land, birds and 
mammals thrived. In the shallow coastal waters and on the 
shores, the bones of these animals were accumulated. 

One may obtain a possible clue to the mode of accumula- 
tion of these remains by a study of the Big Bone Salt Lick 
of Kentucky to which mammals resorted for salt in large 
numbers, and, becoming mired or killed by carnivorous ani- 
mals, their bones have accumulated for ages. Great quanti- 
ties of bones of all kinds are gathered together in this great 
mammalian cemetery. Similar conditions may have existed in 
Florida and South Carolina, and this, added to the excrements 
of birds, may suffice to account for these deposits. 

The recent (1893) disastrous hurricanes on the Gulf Coast 
furnish a suggestion concerning the possible accumulation of 
these land and marine vertebrates. Extensive floods have 
been produced on the low-lying islets of this coast by the 
high water accompanying these storms, and many hundred 



SOILS, CLAYS, FERTILIZERS, ETC. 411 

lives have been lost in consequence. The similar typhoons 
of Asia have caused the destruction of hundreds of thou- 
sands of human lives. These waves, by stranding the larger 
marine vertebrates and at the same time drowning many 
of the land mammals, might readily have caused these 
phosphate beds. Being in the track of many of the West 
India hurricanes, these keys were favourably situated for 
these peculiar conditions; and, while the storms were fre- 
quent enough to cause much destruction, they were not 
frequent enough to completely devastate the region. At 
least, this is the case at present, since man himself inhabits 
the similar islets on the Gulf Coast. 

Secondary changes consisted in grinding the phosphatic 
material to clay under the action of the waves, and later 
the concretionary gathering together of the phosphate of 
lime into layers and nodules. The " river pebbles " repre- 
sent a still later process of concentration by the action of 
river erosion. 

The following tables show approximately the production 
of phosphate of lime in the world and in the United States 
for a series of years : — 

PRODUCTION OF PHOSPHATE OF LIME IN THE WORLD, 1890. 
Metric Tons (2204 Lbs.). 

United States 518,835 

Belgium 280,000! 

Venezuela 60,000 

Chili 2 41,3233 

Canada 23,588 

Great Britain 18,295 

Peru 2 17,0001 

Uruguay 2 9,945^ 

French Guiana 3,500 

1 Estimated. 2 Guano. 3 Exported. 



412 ECONOMIC GEOLOGY OF THE UNITED STATES. 

PRODUCTION OF PHOSPHATE ROCK IN THE UNITED STATES. 
Metric Tons (2204 Lbs.). 

1880 214,229 

1882 337,500 

1884 438,830 

1886 437,579 

1888 . . ■ 455,892 

1890 518,835 

1891 597,589 

1892 651,801 

The value of the output for 1892 was $2,361,219. 

Artesian Wells. 1 

It is usually possible in moist countries to obtain a water 
supply, sufficient for ordinary purposes, by means of wells 
of very shallow depths ; and it is not uncommon in such 
regions to find actual springs outcropping at the surface. 
These rise through joint planes, or along faults in some 
cases, but much more commonly they represent the escape of 
underground water at some favourably situated point on a 
hillside or at the base of a hill. The most common condi- 
tion is where a porous stratum is underlain by an impervious 
layer, such as clay. Water, passing through the porous 
layer, encounters the impervious stratum and flows over it 
in the direction of its dip, and if this stratum outcrops on a 
hillside, a spring is formed. The contact of a deep soil with 
impervious rock, or of any pervious and impervious layer, 

1 A very valuable and comprehensive treatise on artesian wells, prepared 
by Professor R. T. Hill, is published by the Department of Agriculture under 
the title of The Occurrence of Artesian and Other Underground Waters in 
Texas, etc. A paper on artesian wells by Professor T. C. Chamberlain is 
also found in the Fifth Ann. Rept., U. S. Geol. Survey, pp. 125-173. 



SOILS, CLAYS, FERTILIZERS, ETC. 413 

produces the same condition. So common is the association 
between clay strata and springs that such a stratum is usu- 
ally indicated at the surface by a line of springs where it 
outcrops. 

Springs are usually superficial phenomena, and a series 
of droughts, or even a single drought, will frequently 
cause them to disappear, showing how shallow is their ori- 
gin. There are, however, some which are deep seated in 
origin, and these usually rise in permanent and extensive 
now through fissures in the strata. Still another kind of 
large spring is the type which forms in limestone regions 
where much of the drainage is underground. In river 
valleys, and sometimes on plains, these underground streams 
reach the surface as extensive springs. 

Artesian wells are deep-seated springs artificially formed, 
or, more exactly, deep-seated bodies of water tapped by 
artificial borings and rising to, the surface under natural 
hydrostatic pressure. A spring which rises along a fault 
plane closely resembles an artesian well, with the exception 
that its escape to the surface is provided for by a naturally 
formed channel, — the fault plane instead of an artificial 
well. 

The depth of artesian wells varies from a few score to 
several thousand feet, and all depend upon a few simple 
principles. Percolating water divides itself into two parts, 
one portion escaping, after a very short journey, in the form 
of springs or by general seepage, the other portion commenc- 
ing a long underground journey. The latter portion natu- 
rally seeks the easiest paths, and these are in the porous 
rocks. Moreover, under the influence of gravity there is a 
tendency for the water to go deeper into the earth ; but, on 



414 ECONOMIC GEOLOGY OF THE UNITED STATES. 

the other hand, as the depth increases, there is an increasing 
hydrostatic and rock pressure which tends to force the water 
to the surface. This is not sufficient to force it upwards 
through the rocks against gravity unless a channel is fur- 
nished. If the strata are fissured, the water passes to these 
fissures and escapes to the surface naturally ; but if they are 
not, it becomes entombed. 

In the case of horizontal rocks water percolates through 
them, but its progress is retarded by the presence of imper- 
vious layers. The most favourable condition for the accu- 
mulation of water in the strata is in inclined layers, since 
here all of the strata outcrop at some point on the surface, 
and slope downward into the earth with a greater or less 
angle of dip. Where a porous stratum, such as sandstone, 
outcrops, the water that falls upon the area of outcrop 
readily soaks into the ground, and much of it is able to 
begin an underground journey. Naturally, if the dip is 
slight, there is a greater area of outcrop than in the case of 
a steeply inclined bed. Where the sandstone is overlain and 
underlain by an impervious stratum, such as clay or a clay 
rock, the water is prevented from escaping to the surface, as 
it tends to do under the action of the hydrostatic pressure, 
and also from passing through the underlying bed to lower 
layers. The sandstone, therefore, becomes a water-bearing 
stratum, and the water passes down the inclined plane 
between two impervious beds. 

When this stratum is pierced by a well, the water rises, 
theoretically, to the level of the water column in the stratum 
(Fig. 26) ; that is, nearly to the level of the outcrop of the 
stratum at the point of entrance of the water into the earth. 
In reality the water does not rise so high, because of the 



SOILS, CLAYS, FERTILIZERS, ETC. 



415 



3 2 
as. ji 



interference of friction. If, therefore, the outlet of the well 

is above the outcrop of the water-bearing stratum, the water 

rises only part way to the surface ; 

but, if the outlet is below this, the 

water may gush out as a fountain, 

and such wells, artesian wells, are 

usually permanent and have a strong 

flow. 

The slope of the stratum may be 
very gentle, in which case it may be 
tapped for great distances from its 
outcrop without boring to extreme 
depths ; or it may be steep, and then 
an artesian well can be obtained only 
near the outcrop, unless it is driven 
to a great depth. Generally speaking, 
therefore, steeply dipping strata are 
not favourable to the construction of 
artesian wells. 

It not infrequently happens that a 
series of strata, after having dipped 
at a certain angle for some distance, 
become horizontal, and then rise to 
the surface with an opposite dip, 
forming a syncline ; and, if other 
conditions are favourable to the forma- 
tion of artesian water-bearing strata, 
the centre of the syncline is a very 
promising place for an artesian well, 
since the hydrostatic pressure is maintained on two sides 
and the water supply comes from two outcrops, one on 



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3* £+. o* 

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416 ECONOMIC GEOLOGY OE THE UNITED STATES. 

either side of the syncline (Fig. 27). It is frequently 
stated that this is the normal condition for the formation 
of artesian wells ; but such wells are much less common than 
those which are found in strata having a monoclinal atti- 
tude, or, in other words, a dip in only one direction. 

From the above it will be seen that artesian wells are 
purely geological phenomena, and that a knowledge of the 
geology of a country will serve, not only to predict the 



Fig. 27. — Section showing conditions under which artesian wells are found in a 
synclinal trough. A, height of water level; B, porous stratum, bounded 
above and below by impervious strata, and all folded into a syncline ; C, arte- 
sian wells. (After Chamberlain.) 

possibility of finding such supplies of water, but also the 
depth at which it will be found. 

Even in moist climates artesian wells are frequently 
desired for a permanent supply of constantly flowing water ; 
and, in regions of stratified rocks, they can usually be 
obtained with a force sufficient to cause the water to rise 
nearly, if not quite, to the surface. Not infrequently they 
are mineral bearing, and not suited for drinking purposes, 
but supplies of pure water are often obtained. The above 
principles of artesian-well occurrence are of value also in 
obtaining brine from salt-bearing strata, and, as has already 
been stated, the principles apply in part to the petroleum 
wells. 

It is, however, in arid regions that artesian water is of 
most importance in this country, and every year this is 
becoming more true of these regions. There are large 



SOILS, CLAYS, FERTILIZERS, ETC. 417 

tracts which, in their present condition, are absolutely 
unfitted for human habitation, or even for occupation by 
cattle, because there is no drinking-water. One does not 
need to travel very extensively in the arid regions to find 
large tracts where the wild grass has not been touched by 
the herds of cattle with which the more favourably situated 
parts of the region are overstocked. The rains come rarely, 
excepting in a small part of the summer season, and these 
either sink into the thirsty soil or flow away through chan- 
nels which are usually dry. 

The discovery of artesian water in such places opens up 
an otherwise inhospitable region to settlement. Even where 
cattle-raising is possible, agriculture is out of the question, 
because of the aridity and the absence of water for irri- 
gation, the only supply being from scattered springs, with 
a small flow, near the mountains. In the mountains a suffi- 
cient amount of rain falls for some crops, but the country is 
generally too rugged for cultivation, and the water, excepting 
from the larger ranges, does not escape beyond the margin 
of the mountainous tracts, being either evaporated or soaked 
into the ground. Since the mountain-forming rocks extend 
beneath the plains, artesian water may be found even where 
the surface is very arid. Moreover, on the less arid plateaus 
sufficient water falls, at certain seasons, to cause under- 
ground water-bearing strata. When these have been found 
at no great depth, large tracts which were formerly desert 
and uninhabited are now dotted with small farms irrigated 
with artesian water. One of the future possibilities of the 
arid regions consists in the discovery and development of 
artesian water-bearing belts, a work which is already begun, 
but hardly more than begun. 



418 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Mr. F. H. Newell 1 states that in the census year there 
were 8097 artesian wells in the western half of the country, 
3930 of which were used for purposes of irrigation. Cali- 
fornia had 3210; Utah, 2524; Colorado, 596; Texas, 534; 
and South Dakota, 527 such wells. The average area irri- 
gated per well was 13.21 acres, and in California and Colo- 
rado over 18 acres. The total number of acres thus irrigated 
was 51,896, of which 38,378 were in California. The total 
8097 wells represent an investment of about $1,988,461. 

Mineral Waters? 

A very important industry in this country is the utilization 
of waters which, having dissolved certain mineral constitu- 
ents from the rocks, issue from the earth either through 
natural channels, in the form of springs, or from artificially 
formed wells. These mineral waters possess some properties 
which render them of value for medicinal or other purposes. 
Peale, in the census report above referred to, classifies min- 
eral waters as thermal and non-thermal, the latter being cold, 
and the former either tepid, warm, or hot. The thermal 
springs are generally, though not always, found in regions 
of recent or present volcanic activity, and are often one of 
the indications of this activity, — in this country one of the 
indications of dying volcanic action. All waters issuing 
from the earth contain mineral in solution ; and it is this 
which gives to it medicinal qualities, chiefly that of a tonic. 
No such waters are more common than those containing 

1 Eleventh Census Bulletin, No. 193, Artesian Wells for Irrigation. 

2 A very valuable discussion and classification of the mineral waters in 
the United States, from which this summary is chiefly extracted, is found in 
the Eleventh Census Report, on Mineral Industries, pp. 779-787. 



SOILS, CLAYS, FERTILIZERS, ETC. 419 

iron ; but there are numerous other kinds of mineral waters, 
such as those which contain sulphur, in the form of sul- 
phuretted hydrogen, lithia, manganese, and many other sub- 
stances. Many mineral springs are not utilized, and some 
which are used are of little value. 

There are two classes of materials in mineral waters, 
gaseous and solid substances, although it frequently happens 
that both of these constituents are present in the same 
spring. It is upon the basis of the solid constituents that 
Peale constructs his classification, omitting the temperature, 
since there is every gradation from hot to cold springs, 
and since there is no necessary difference between the con- 
stituents of the two. Each group may be represented by 
thermal and non-thermal types, the term thermal being 
applied to those whose temperature is above 70° Fahr. The 
gaseous constituent is used for minor subdivisions. 

This classification of mineral waters cannot be given here 
in detail, but in general the scheme is as follows : (1) Alka- 
line springs, when they contain carbonates, "whether of 
alkalies, alkaline earths, alkaline metals, or iron alone " ; 
(2) alkaline saline springs, those in which carbonates are 
mixed with sulphates or chlorides ; (3) saline springs ; 
(4) acid springs, which include the sour water containing 
alum, sulphuric acid, etc. There are many subdivisions 
based upon this general scheme. 

Some of these springs furnish water for bottling, while 
others are used entirely at the point of issue. It is difficult 
to obtain exact information concerning the number and value 
of the mineral springs of the country, but the following table 
gives the approximate statistics. In 1891 the list of com- 
mercial mineral springs in the country numbered 288. 



420 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



PRODUCTION OF MINERAL WATERS IN THE UNITED 
STATES, 1891. 



States. 


Gallons. 


Value. 


New York 

New Hampshire 

Virginia 


2,779,472 
960,000 
534,293 
2,882,117 
2,228,575 
334,533 
481,038 
841,062 


$796,047 
502,000 
215,392 


Wisconsin 

Michigan 

California 

Colorado 

Massachusetts 


184,133 
149,773 
135,959 
133,222 
115,591 


Total for the United States . . 


18,392,732 


$2,996,259 






It will be noticed that there is no necessary relation be- 
tween the number of gallons produced and their value, since 
much depends upon the demand for particular classes of 
mineral water. 



MINERAL-WATER PRODUCTION OF THE UNITED STATES. 



Year. Gallons. 

1880 2,000,000 

1885 9,148,401 

1891 18,392,732 



Value. 

$500,000 
1,312,845 
2,996,259 



The industry is thus a rapidly growing one. Our imports 
of natural mineral waters, in 1891, were 2,019,833 gallons, 
valued at $392,894. 



CHAPTER XVIII. 

PRECIOUS STONES, ABRASIVE MATERIALS, SALT, MISCELLA- 
NEOUS MINERALS, AND GENERAL SUMMARY OF MINERAL 
PRODUCTION. 

Precious Stones. 1 

The production of precious stones in this country has 
never attained especial prominence, although nearly all gems 
have been occasionally found. Turquoise and pearls are the 
only gems produced in this country in quantities sufficient 
to call for especial consideration; but, since there seems 
every reason to expect that valuable stones may yet be found 
in our western region, some mention will be made of these 
even though at present the production is unimportant. In 
prehistoric times turquoise was obtained by the Indians from 
Los Cerrillos, New Mexico, and beads of this mineral are 
often found with their implements. These turquoise veins 
are still worked, and recently other veins have been dis- 
covered in the Burro Mountains, Grant County, New Mexico, 
some of the gems from these mines being equal in colour to 
the best oriental turquoise. 

During the present year (1893), turquoise has been dis- 
covered in the Jarilla Mountains, in Dona Ana County, New 

1 The subject of precious stones is treated fully by G. F. Kunz in Gems 
and Precious Stones of North America, by E. W. Streeter in Precious 
Stones and Gems, and also in the Eleventh Census Report on Mineral Indus- 
tries, and the reports on the Mineral Resources of the United States, Day, 
U. S. Geol. Survey. 

421 



422 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Mexico, and it is predicted that this will prove of great 
value. As in the case of the Grant County gems, the 
occurrence is in association with intrusive trachyte, the min- 
eral being the result of an alteration of the kaolin which 
existed in the veins. The turquoise grew, as it were, in the 
kaolin, it being a hydrous phosphate of aluminum. All of 
these turquoise veins were originally worked by the Indians, 
and their discovery was due to this fact. But as an illus- 
tration of the lack of knowledge of the rarer minerals on 
the part of the prospectors, it may be pointed out that the 
Jarilla deposit was overlooked on the assumption that it 
was a copper stain. 

Pearls are frequently found in fresh-water clams belong- 
ing to the genus Unio, and some of these are of value. 
Particularly valuable finds have been made in Wisconsin, 
and Kunz states that pearls of good quality are more liable 
to be found in creeks which flow through a limestone country. 

Precious stones, particularly sapphire and diamond, have 
been occasionally found in the gold-bearing gravels in vari- 
ous parts of the west, but, until very recently, no systematic 
efforts have been made to obtain them, nor has any success 
attended the efforts to find their source in the rocks. Re- 
cently systematic work has been carried on for the recovery 
of sapphire from the gravel bars in the Missouri River east of 
Helena, Montana. These are being carefully washed for 
gems, but only a small degree of success has rewarded the 
efforts, since the few gems which are found have not the red 
colour of ruby, nor the blue of sapphire, but range through 
lighter colours of blue, red, green, and yellow. Sapphire 
crystals have been found in an andesite dike crossing the 
slates upon which the gravels rest, and the source of the 



PRECIOUS STONES, ABRASIVE MATERIALS, ETC. 423 

gems may have been a similar rock, but no thoroughly scien- 
tific study has been made of the region and its possibilities. 
At Corundum Hill, North Carolina, some fairly good sap- 
phires are occasionally found. 

A few diamonds have been discovered in gravels in 
North Carolina, Georgia, and California, in well-defined 
areas, but they have not been traced to their source. 

Garnets, valuable for gems, have been found in several 
parts of the country, but the principal supply comes from 
the Navajo Indian Reservation, where they are obtained 
from ant-hills. In 1890 opal was discovered in the state of 
Washington filling amygdaloidal cavities of varying size in 
basalt, and operations have been pushed with the result of 
producing some good-sized stones equalling those of Hungary 
and Australia. Tourmaline gems are found in the Colorado 
desert, Rumford, Maine, and elsewhere, and some very beau- 
tiful titanite or sphene crystals of a beautiful yellow colour 
have been obtained from the Tilly Foster mine in Putnam 
County, New York. 

Quartz, either in the transparent condition, or coloured, 
or containing inclusions, is frequently used for cheap jewelry, 
and this industry is of considerable importance, particularly 
in places visited by numbers of tourists, such as the Hot 
Springs of Arkansas. In several parts of the west there 
are fossil forests in which petrified trees are composed of 
agate or jasper, often beautifully banded, and these are made 
use of extensively for the manufacture of ornaments and jew- 
elry. Satin spar or fibrous gypsum is also cut into cheap 
ornaments and jewelry, and there are numerous other minerals 
used for similar purposes. Several gems, besides those above 
mentioned, have been found sparingly in the United States. 



424 ECONOMIC GEOLOGY OF THE UNITED STATES. 

The following table furnishes an approximate statement of 
the value of the precious stone production of this country : — 

PRODUCTION OF PRECIOUS STONES IN THE UNITED STATES. 



Stones. 


1884. 


1886. 


1888. 


1890. 


1891. 


Turquoise . . 
Sapphire . . . 
Quartz 






$2,000 

1,750 

11,500 

140,000 

12,000 

10,000 
4,000 
2,000 

800 


$3,000 

750 

11,500 

40,000 

7,000 

10,000 
3,250 
5,500 

60 


$3,000 

500 

11,150 

75,000 

4,000 

5,000 
3,500 


$28,675 

6,725 

14,000 

9,000 

2,225 

5,000 
2,308 
2,250 
6,000 


$150,000 
10,000 
10,000 
6,000 
5,000 
5,000 
5,000 
3,000 
3,000 
2,000 


Gold quartz . . 
Smoky quartz . 
Opal .... 




Catlinite . . . 
Garnet 




Tourmaline . . 
Agatized wood . 
Diamond . . 




Total . . . 






$222,825 


$118,850 


$139,850 


$118,833 


$235,300 







The above table, which is in large part merely a rough 
estimate, probably does not represent the true value of the 
output of gems and precious stones, since large quantities 
are sold at the point of production, and cut by local jewellers, 
without any record being kept. Moreover, there are many 
mineral collectors who purchase precious stones for private 
and public collections, some of them purchasing the entire 
output of some of the smaller producing localities. It is not 
improbable that the true value of the industry is fully double 
that stated in the above table, but, nevertheless, the precious 
stone production of the United States is extremely limited, 
and the country is probably by no means up to its possible 



PRECIOUS STONES, ABRASIVE MATERIALS, ETC. 425 

capacity as a producer of these minerals. Now that the west 
has entered upon a stage of more minute and intelligent 
exploration, it need not be surprising if gems of value are 
found. When we compare our precious stone production 
with our consumption of cut and uncut gems, which in 1891 
was valued at over $12,700,000, and with the output of 
diamonds from the Cape of Good Hope fields, which in 1890 
exported £4,162,073 sterling worth, we plainly see the lack 
of importance of the United States in this respect. 

Abrasive Materials. 
General Statement. — There are two classes of materials 
which serve for abrasive purposes : those used as a powder or 
a sand, and those used as stones. In the first class are grouped 
sand, diamond, corundum, emery, infusorial earth, and some 
minor substances ; and, in the second class, millstones, grind- 
stones, and whetstones. Sometimes stones of the latter class 
are prepared artificially, by the manufacture of a rock con- 
sisting in part of powdered or granular abrasive substances ; 
but more commonly they are naturally formed rocks. Sand 
is used for abrasive purposes in polishing and sawing certain 
stones, such as marble, the sand being fed to a straight- 
edged steel saw, which moves back and forth on the stone, 
and uses the sand for cutting edges. Diamond dust, obtained 
from the waste made in cutting diamonds, and from black 
and imperfect diamond bort, is also used for sawing hard 
rocks and minerals, chiefly in the preparation of gems and 
the manufacture of ornaments from hard rocks and minerals. 
Being the hardest known mineral, it is of great value for 
these purposes. Corundum and emery are used, in the form 
of granular fragments, and as a fine Hour-like powder, for 



426 ECONOMIC GEOLOGY OF THE UNITED STATES. 

smoothing and polishing purposes, as, for instance, in pol- 
ishing granite and other rocks, and also in the form of 
artificially made wheels for grinding purposes. Infusorial 
earth is also used for polishing, but for a finer grade of work 
than the above materials. 

Infusorial Earth. — Certain animals, known as Infusoria, 
and plants belonging to the group of Diatoms, secrete shells 
or tests of silica, and when they die these durable parts 
are left behind. When in particular bodies of water 
these organisms are the predominant forms of life ; having 
durable shells they tend to accumulate in beds, forming 
diatomaceous or infusorial earth. These forms of life are 
particularly abundant in fresh-water ponds ; and conse- 
quently their remains are commonly found in the swamps, 
which are filled-up lakes, of the glacial belt in New Eng- 
land and other northern states. Where these ponds were 
small, and their banks bordered with reeds and other 
forms of vegetation, very little sediment entered, and the 
accumulations were principally organic, and the infusorial 
beds comparatively pure. A thin layer of this white, pow- 
dery earth is found in excavations in many swamps, but it is 
usually not sufficiently abundant to be of value. Infusorial 
earth, in this country, is principally obtained from Pope's 
Creek, Maryland, but California, New Hampshire, and New 
Jersey also produce some. There is not an extensive demand 
for this substance, and consequently the output is limited. 
It has served, as an absorbent, in the manufacture of dyna- 
mite ; but wood pulp is replacing it for this purpose. In 
the form of a soap or a powder, it is used as silver polish 
and for other cleansing purposes, and also in the formation 
of a glaze for bricks. 



PRECIOUS STONES, ABRASIVE MATERIALS, ETC. 427 

Corundum and Emery. — These minerals differ from each 
other very slightly, the former being oxide of aluminum, 
and the latter being corundum mixed with iron oxide. The 
former is, therefore, harder and more durable, and hence 
more valuable, it being the hardest of the minerals which 
are common enough for extensive use, ranking next to dia- 
mond in the mineralogical scale of hardness, diamond being 
10, corundum 9 (in its pure form sapphire). Emery is 
found in the metamorphic rocks at Chester, Massachusetts ; 
and corundum is produced at Laurel Creek in Georgia and 
Corundum Hill in North Carolina. It occurs here at the 
contact of gneiss and serpentine, the latter having resulted 
from the alteration of an olivine rock. There are other 
minor localities for these minerals. Practically all of the 
corundum used in the country is of domestic production, but 
much of the emery is imported, our imports in 1891 having 
amounted to 1104,199. 

Grindstones and Buhrstone. — Grindstones are made of a 
firm, gritty sandstone, and these are principally produced 
from the Berea grit of Ohio and Michigan, although Cali- 
fornia and South Dakota also produce some. Although 
some of the grindstones used in this country are imported, 
the greater number are of domestic production. 

The industry of buhrstone or millstone production has 
rapidly decreased since the introduction of the roller process 
of grinding grain, but they are still used in many of the 
small grist mills, and for grinding cement, paint, gypsum, 
etc. Stones for these purposes are found in this country ; 
but the grist mills still using buhrstones prefer the French 
buhr, which is of superior quality to any produced in this 
country. A buhrstone must be fine grained and very com- 



428 ECONOMIC GEOLOGY OF THE UNITED STATES. 

pact, much more so than grindstones ; but it must not glaze 
too readily, nor, on the other hand, should its texture be so 
loose that particles rub off, as in the case of grindstones. 
A gritty quartzite or a quartz conglomerate are the rocks 
best adapted for this purpose ; and in this country the chief 
supply comes from Ulster County, New York, and, in smaller 
quantities, from Pennsylvania and Virginia. In 1891 we 
imported $24,039 worth of millstones. 

Oilstones and Whetstones. — Oilstones and whetstones are 
chiefly of domestic production. Since 1823 New Hampshire 
has been the seat of the scythe-stone industry, a valuable 
grit for this purpose being found in a mica schist in Grafton 
County. Whetstones are also found in Massachusetts and 
Vermont. The western grindstone grits furnish some 
scythe-stones; but they are more gritty and coarser, and 
hence inferior to those produced by the New Hampshire 
company, which also operates the Massachusetts and Ver- 
mont quarries, and exports considerable quantities to Europe. 

Oilstones are of a still finer texture, and these are also 
found in New Hampshire ; but the most important seat 
of the oilstone production is in Garland County, Arkansas, 
where there are extensive beds of novaculite, of Palaeozoic 
age, occurring stratified with shales and limestones in very 
much folded strata. These deposits were first made to 
produce commercially in 1840, although extensive quarries 
were worked for implements by the aborigines. These 
stones, known as Washita and Arkansas oilstones, are 
recognized as the best in the world for sharpening fine 
tools, and they are extensively used for this purpose both 
in Europe and the United States. The most important 
quarries are situated near the Arkansas Hot Springs, and 



• PRECIOUS STONES, ABRASIVE MATERIALS, ETC. 429 

Griswold states x that they are actually deposited sediments 
of fine-grained quartz, instead of a chemically precipitated 
deposit, as was formerly believed. There are immense quan- 
tities of novaculite in this region, but the grade is very 
variable, and some of it is quite inaccessible at present. 

An oilstone, known as the Hindostan, is quarried in 
Orange County, Indiana. It is a very compact sandstone, 
and, although very good, does not equal the Arkansas 
novaculite; but is more cheaply quarried and fashioned, 
and hence is sold at a lower price. A more coarsely grained 
sandstone, known as the Shoemakers' sandstone, is also ob- 
tained from Indiana, and, until recently, this has been of 
considerable value in shoemaking ; but the introduction 
of improved machinery has caused the demand to rapidly 
decrease. 

Statistics. — In 1891 this country exported $51,500 worth of 
whetstones, and the following table shows the production of 
the various abrasive materials for a series of years : — 

PRODUCTION OF ABRASIVE MATERIALS IN THE UNITED 

STATES. 



Materials. 


1880. 


1885. 


1890. 


1892. 


Infusorial earth . . . . 
Corundum and emery 

Grindstones 

Buhrstones 

Whetstones and oilstones, 


$45,660 

29,280 

500,000 

200,000 

8,000 


$5,000 
108,000 
500,000 
100,000 

15,000 


$50,240 
89,395 

450,000 
23,720 
69,909 


$20,000 
88,000 

500,000 
16,000 

150,000 


Total 


$782,940 


$728,000 


$683,264 


$774,000 



1 The novaculite of this country, and the industry in general, are fully 
described by L. S. Griswold in a valuable Monograph entitled Whetstones and 
Novaculites of Arkansas, Ann. Bept. Ark. Geol. Survey for 1890, Vol. III. 



430 ECONOMIC GEOLOGY OF THE UNITED STATES. • 

Salt. 

Our supply of salt comes either from brine or from 
deposits of rock-salt. At several places in California salt 
is obtained by evaporating ocean water ; but this source is 
not as important as might at first be supposed, since more 
concentrated solutions occur elsewhere. In various parts 
of the Cordilleras salt lakes exist, and there is every grada- 
tion in this region, from fresh-water lakes to deposits of 
rock-salt, which have resulted from the evaporation of 
salt lakes. There are several salt works located upon the 
shores of Great Salt Lake, in Utah, and in Nevada, upon 
the shores of the smaller salt lakes of that state. The 
salt thus obtained by solar evaporation is used principally 
for local purposes, particularly in the chlorination process 
of reducing ores. Some of these lakes have crusts of salt, 
and, in some cases, in all the arid regions of the west, the 
water has entirely disappeared under the influence of the 
arid climate, and here the ranchmen are able to obtain 
their supply of salt at the surface, from beds of rock-salt 
produced by the natural evaporation of dead seas. 

'Rock-salt deposits, now buried in the earth, have resulted 
from the same process as that just described, and these 
are found stratified in rocks of various ages from the Silurian 
to the present. Water, in its passage over and through 
the earth, dissolves many minerals, the most common being 
salt. 1 When these waters, which contain so little salt that 
they seem fresh, enter an enclosed sea without an outlet, 
the fresh water is evaporated and the salt is concentrated, 
until, finally, after a long period of time, it may accumu- 

1 The mineralogical name of salt is halite. 



PRECIOUS STONES, ABRASIVE MATERIALS, ETC. 431 

late in a solid mass of rock-salt either at the bottom of 
the lake, or in place of the lake, if all of the water is 
evaporated. Many impurities usually occur with rock-salt, 
either disseminated through it or concentrated into layers. 
These represent the impurities dissolved in water with the 
salt. Other chlorides, particularly those of calcium and 
potassium, gypsum, iron, and sedimentary deposits of clay 
or sandstone, are some of the common impurities which 
must be separated. 

A bed of rock-salt of considerable extent occurs in the 
Tertiary deposits on Petit Anse island in Louisiana, where it 
was discovered, during the Civil War, beneath the site of 
some salt wells which had been known for a long time. 
In western New York beds of rock-salt occur in the 
Silurian over a wide area, in Kansas in the Triassic, and 
in Texas in the Permian rocks. Some of these rock-salt 
deposits are actually mined, but some are worked as brines, 
water being allowed to enter the salt beds from below, 
through artificial borings; and, after dissolving the salt, 
the water is brought to the surface either through natural 
artesian wells or by pumps. Some of these beds are un- 
doubtedly dried-up salt lakes, but some may be salt deposits 
which have accumulated in shallow coastal lagoons or upon 
salt marshes along some ancient shore. 

However, much of the salt of the country is made from 
natural brines which occur scattered through rocks of all 
ages, and are obtained from wells, either by pumping or as 
artesian water. The most common mode of occurrence is in 
beds of sandstone, capped and underlain by more impervious 
beds. Some of this salt may have been originally built into 
the rocks when they were deposited in the ocean ; some may 



432 ECONOMIC GEOLOGY OF THE UNITED STATES. 

represent beds of rock-salt subsequently dissolved ; and some 
are apparently derived in the same manner as petroleum and 
natural gas, — namely, by accumulation in a porous stratum 
from some outside source. Associated with the salt in the 
brine are the same minerals which are found in rock-salt; 
and brines are also frequently associated with petroleum and 
natural gas. Some of the impurities, such as gypsum, are 
injurious ; and one of the chief problems in salt manufacture 
is how to remove all of these substances without injuring the 
salt or interfering with its evaporation. 

Our salt supply comes chiefly from the Salina group of 
the Silurian in New York and from the Carboniferous in 
Michigan; but other states and other ages of rocks are also 
saliferous. The salt is obtained in some places by solar 
evaporation, in large shallow pans ; in others, by artificial 
heat obtained by burning wood, coal, or natural gas. The 
price of this mineral is extremely low, and it is produced 
at a profit only where it can be obtained very easily and 
evaporated cheaply. This is very strikingly shown by the 
fact that sea water can rarely be evaporated, even in arid 
regions, and made to yield salt at a profit. Nevertheless, 
both in this country and in Europe this is done in certain 
very favourably situated localities. 

The distribution of the salt supply is shown in the follow- 
ing table ; but this does not represent the distribution of 
salt, for there is probably vastly more in the Tertiary and 
recent strata of the Cordilleras than in any other part of 
the country, but it is too far from the market to be of 
value. Very pure salt can be obtained by the wagon-load 
in scores of places in the far West. 



PEECIOUS STONES, ABRASIVE MATERIALS, ETC. 433 



PRODUCTION OF SALT IN THE UNITED STATES. 



States. 


1883. 


1885. 


1887. 


1889. 


1892. 


New York . . 


$680,638 


$874,258 


$936,894 


$1,136,503 


$2,200,000 


Michigan . . 


2,344,684 


2,967,663 


2,291,842 


2,088,909 


1,906,027 


Kansas . . . 








202,500 


698,395 


Utah. . . . 


100,000 


75,000 


102,375 


60,000 


295,000 


Ohio .... 


231,000 


199,450 


219,000 


162,500 


276,000 


West Virginia, 


211,000 


145,070 


135,000 


130,000 


166,800 


California . . 


150,000 


160,000 


140,000 


63,000 


125,000 


Louisiana . . 


141,125 


139,911 


118,735 


152,000 


81,000 


Total . . . 


$4,251,042 


$4,825,345 


$4,093,846 


$4,195,412 


$5,879,222 



New York has rapidly increased its output, and Kansas 
has shown a remarkable increase since 1888, when salt first 
began to be produced there. At the same time, Louisiana 
and Michigan have decreased; and in ten years there has 
been a very slight total increase for the country. Our pro- 
duction of salt is practically what we consume, although we 
export about $30,000 worth a year ; and in 1892 we imported 
$768,734 worth, chiefly for special purposes. The output for 
1892 represents 11,585,734 barrels of 280 pounds each. Aside 
from a certain increase in demand for this mineral in the 
reduction of ores and in the manufacture of caustic and 
baking soda, the increase in the salt industry must be depen- 
dent upon the increase in population, its consumption for 
cooking, table, and curing purposes being the most important 
uses of the mineral. 



434 ECONOMIC GEOLOGY OF THE UNITED STATES. 

OUTPUT OF SALT IN THE WORLD, 1891. 
Metric Tons (2204 Lbs.). 

Great Britain 2,077,072 

Russia l,400,000 x 

United States 1,300,107 

Germany 666,793 

Spain 225,870* 

Hungary 159,898 

Canada 45,021 

Italy 31,285 

Colombia . 21,644 

Bromine. 

This element is not found free, but in the form of bromides, 
and the chief source is from rock-salt and salt water. It is 
produced as a by-product in the manufacture of salt in West 
Virginia, Michigan, and some other salt regions. During the 
evaporation of salt, it becomes concentrated, together with 
some other substances, in the bittern or mother liquor, from 
which it is extracted. Its chief use is for chemicals, in the 
manufacture of an aniline colour (eosene) and, in smaller 
amounts, as a disinfectant. In the past twelve years the 
product of bromine in this country has varied somewhat; 
but in 1892, 379,480 pounds were produced, valued at $64,512. 

Borax. 

Among the other substances found associated with salt 
are borax, soda, and gypsum, the latter of which is described 
in the preceding chapter. Borax exists in the alkaline flats 
of the arid regions which contain valuable stores of alkaline 

1 Estimated. 2 Exported. 






PRECIOUS STONES, ABRASIVE MATERIALS, ETC. 435 

substances, the greater part of which no attempt has ever 
been made to utilize. In Tuscany this substance occurs in 
hot springs, while in Hungary it is obtained from the rock- 
salt ; but in our country the source is the beds of desiccated 
lakes in the desert regions of Nevada and California. The 
" salines," which contain borax, in the west, probably received 
their supply from hot springs resulting from the neighbour- 
ing volcanic activity which was very well developed in the 
Great Basin during the period of desiccation. The minerals 
are borate of soda and of lime, mixed with clay, gypsum, 
salt, and other impurities. There is also borax in fissure 
veins in California, probably deposited in the tube of a hot 
spring similar to the Tuscan springs ; and the industry of 
borax production in that state has rapidly increased since the 
introduction of deep mining. Aside from the European 
localities, borax is produced also in Thibet, Asia Minor, and 
Chili, in dried lake bottoms similar to those of the Great 
Basin of the Cordilleras. 

The original source of borax is probably in all cases vol- 
canic emanations, the hot springs of Tuscany illustrating 
the active stage in its production. These, flowing into the 
waters of the salt lakes, caused borax to accumulate in the 
same manner that salt and gypsum accumulate in the same 
places. In the west the borax permeates the soil, as does 
ordinary alkali ; and in favourable situations, a crust forms 
upon the surface. After this has been removed, a new 
deposit commences to form by the solution of the mineral 
in percolating waters ; and its rise to the surface by capillary 
action forms a crust by the subsequent evaporation of the 
boracic waters. After five or six years a new crust is 
formed ; but this naturally does not equal, in thickness, the 



436 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



original crust which has been accumulating for ages. It is 
removed, dissolved, and evaporated ; and the process is 
repeated until crystals of nearly pure borax are formed. 

Borax is used in welding, since it forms fusible salts with 
most metallic oxides, and it is also used in glazing brick, 
chinaware, etc., as well as in the manufacture of enamel for 
ironware, and for the gloss given to starched linen in laun- 
dry work. As an antiseptic it is important, and it is also 
used in dyeing, for sanitary purposes, and in drugs. Our 
consumption of borax about equals the production, which is 
given in the following table : — 

PRODUCTION OF BORAX IN THE UNITED STATES. 
Pounds. 



Year. 


California. 


Nevada. 


Total. 


1864' 


24,304 


.... 


24,304 


1865 


251,092 




251,092 


1875 


2,336,000 


2,804,000 


5,140,000 


1880 


1,219,948 


2,640,800 


3,860,748 


1885 


1,885,300 


5,586,104 


7,471,404 


1890 


6,402,034 


5,487,794 


11,889,828 


1892 ..... 


11,596,574 


2,646,525 


14,243,099 



Since 1864 the total production of the United States has 
been 128,539,190 pounds, and the price has steadily decreased, 
with some fluctuations, having remained, however, for the 
past four years 7J cents a pound in New York. The value 
of the borax output at the place of production was, in 1892, 
$925,810. 



PRECIOUS STONES, ABRASIVE MATERIALS, ETC. 437 

Natural Soda, 
This is obtained from the alkaline substances which are 
so abundant in arid regions, such as those of the Great 
Basin, the deserts of Africa, Asia, and South America, where 
it occurs in the form of carbonate and bicarbonate of soda 
mixed with clay and various chemical impurities. The 
alkali coats large areas with a snow-white, efflorescent 
deposit, and sometimes with a thick crust. There are vast 
quantities of these substances in the deserts, alkali flats, and 
alkaline pools of the west ; but as yet little has been done to 
extract them, and only a small amount is produced. This is 
probably an industry which will assume marked importance 
in the future, now that the knowledge of methods of extrac- 
tion has improved and means of cheap transportation are at 
hand. 

Magnesite. 

This mineral, which is a carbonate of magnesia, occurs in 
a number of places in California, and possibly elsewhere in 
the Cordilleras. It resembles unglazed porcelain, being 
hard, fine grained, and white. There are several modes of 
occurrence, one being in a vein from five to seven feet thick 
in Childs Valley, while elsewhere it is generally bedded with 
talcose slates, serpentines, and magnesian carbonates or dolo- 
mites. TJntil recently no use has been made of this mineral, 
but within a few years experiments have been made with 
the idea of introducing it; and already it is being used as 
a substitute for chlorine, as a bleacher, in the manufacture 
of paper from wood pulp, for which purpose it is said to be 
better suited, as well as cheaper, than chlorine. Other uses 
are also made of it, and it is expected that it will be possible 



438 ECONOMIC GEOLOGY OF THE UNITED STATES. 

to ship the mineral as far east as Pittsburg and compete 
with the foreign magnesia used in the manufacture of basic 
steel. 

Sulphur. 

Sulphur is obtained from three sources, — iron pyrite, 
which has already been described, 1 from the waste calcium 
sulphide produced in the alkali works, and from native sul- 
phur. Native sulphur is known to exist in various parts of 
the west, but nearly all of these deposits are so inaccessible, 
and the cost of transportation to the market so great, that 
they are not exploited. At present the total supply pro- 
duced in this country comes from Utah and Nevada. Out- 
side of the United States sulphur is found in numerous 
places, chiefly in volcanic regions. Extensive deposits are 
known to exist in Japan, but they are not favourably situated 
for profitable production, and our principal supply comes 
from the island of Sicily, which has produced this mineral for 
several centuries. It is obtained here from various mines, 
scattered over a wide area, and worked to a considerable 
depth by very crude and antique methods. Since 1831 
there has been produced from this district nearly 13,000,000 
tons of sulphur, valued at not far from $350,000,000. 

At first thought the explanation of the origin of sulphur 
seems simple, particularly when it occurs in volcanic regions, 
where emanations of sulphur vapor are commonly associated 
with eruptions of lava. Since sulphur deposits are so com- 
monly associated with recent volcanic rocks, there is good 
reason to believe that they are frequently the result of 
this association. But the breaking up of sulphuretted 

ip. 300. 



PRECIOUS STONES, ABRASIVE MATERIALS, ETC. 439 

hydrogen, produced from the decomposition of gypsum or of 
organic remains, will also form sulphur deposits, and such 
appears to be the origin of at least some of the Sicilian sul- 
phur and of a bed of sulphur which occurs stratified with 
sedimentary rocks in a region no less remote from volcanoes 
£han western Louisiana. 

The demand for native sulphur is decreasing, although 
the uses to which it is put are increasing. This is due to 
the increasing use of pyrites in the manufacture of sulphuric 
acid, and to the production of sulphur from the calcium sul- 
phide, which was formerly a waste product in the manu- 
facture of alkalies. The statistics of the production of 
iron pyrite are given in a previous chapter. 

We have in this industry the rather anomalous condition of 
abundant supplies at home, but practically no home produc- 
tion, notwithstanding a heavy demand for brimstone at a price 
varying from $22 to $30 a ton. There are other minerals of 
minor importance which illustrate the same peculiarity; but 
in most cases where our mineral supply is good our production 
is large. These peculiarities are generally, as in the present 
instance, the result of a failure of railroad transportation to 
compete with ocean transportation, combined with certain 
difficulties of mining and transporting materials in our 
sparsely settled western territory. There are some reasons 
to hope that the sulphur deposits of the west will eventually 
become of importance, but at present only those of Utah are 
of value. 

Sulphur is used in the manufacture of sulphuric acid, 
matches, gunpowder, and many minor substances, as well as in 
its native condition in medicine and for other purposes. In 
1892 our production of this mineral amounted to 1825 short 



440 ECONOMIC GEOLOGY OF THE UNITED STATES. 

tons, valued at 154,750, while we imported, chiefly from 
Sicily, 100,711 long tons, valued at 12,189,307. During 1890 
Sicily exported 344,763 tons, and during 1891, 293,823 tons. 



Fluor ite. 

This mineral is not uncommon, as a veinstone, in various 
parts of the world, and it is found sparingly in granites and 
metamorphic rocks ; but until within a few years it has not 
been considered of much value. Now, however, it is intro- 
duced into the reduction of some of the refractory ores, for 
which it serves as an excellent flux; and it is also used in 
the manufacture of opalescent glass, in the production of 
hydrofluoric acid, and for other minor purposes. In this 
country the only source of fluorite is the galena-bearing 
limestones at Rosiclare, Hardin County, in the southern 
part of Illinois. Formerly these deposits were worked for 
lead, and the fluorite was a waste product, but now the re- 
verse is true. The mineral occurs in true fissure veins, which 
have been traced for -a distance of several miles. Fluorite 
is not an uncommon mineral in altered dolomitic limestone, 
and it is possible that the above deposits will change in 
character when the limestones are passed through. 

The output of fluorite from this region has more than 
doubled in the past ten years, and in 1892 amounted to 9000 
short tons, valued, at $54,000. No fluor-spar is imported, 
but it is obtained as a by-product in the reduction of cryolite 
to aluminum and sodium. This source is decreasing, how- 
ever, with the introduction of bauxite as a source of alumi- 
num. In 1892, 8155 long tons of cryolite, valued at $73,847, 
were imported into this country. 



PRECIOUS STONES, ABRASIVE MATERIALS, ETC. 441 

Graphite. 

Plumbago, or graphite, one of the pure forms of carbon, 
occurs in metamorphic rocks, particularly in limestones, 
where it is undoubtedly the result of the metamorphism of 
carbonaceous substances of organic origin. The same is 
true of the graphitic coals of Rhode Island, where the Car- 
boniferous coal has been metamorphosed almost to the stage 
of graphite, and locally actually to this condition. The 
Rhode Island graphitic anthracites are used to some extent 
in the manufacture of crucibles and stove-blacking. Graphite 
has also been mined in Pennsylvania, New Jersey, Michigan, 
and Wyoming ; but the only important American source of 
this mineral is at Ticonderoga, New York, where, in the 
metamorphic rocks, there is a vein of sufficient purity to be 
used in the manufacture of lead-pencils. This mineral is 
found in Japan, Russia, Canada, Germany, Austria, and 
Ceylon, the bulk of our supply coming from the latter 
region. In every case the source being rocks of metamorphic 
origin, this fact has led some to hold that for this reason 
we must consider them to be of sedimentary origin and 
the graphite to be inorganic in origin; but this is a mere 
assumption. 

In 1891 the output of graphite in the United States was 
1,559,674 pounds, valued at 1110,000, and in the same year 
we imported $555,080 worth of plumbago. The better qual- 
ities of graphite are used in the manufacture of lead-pencils, 
and much is also used in the preparation of lubricants, while 
the poorer qualities are manufactured into stove polish, cru- 
cibles, paint for the protection of iron, and other similar 
purposes. 



442 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Lithographic Stone, 

Although this country imports about 8100,000 worth of 
unengraved lithographic stone each year, none is produced 
here. This is probably not because there is none in the 
country, but rather because its occurrence has not been 
detected. There are, in many places, rocks which very 
closely resemble lithographic stone, but these have not the 
fineness of quality which fits the Solenhofen stone so well 
for lithographic purposes. This is a compact, homogenous, 
fine-grained limestone, of gray or creamish colour, found at 
Solenhofen in Germany. It varies somewhat in texture, and 
colour, and some is suited only to low-grade work. Litho- 
graphic stone is found elsewhere in Europe, but in no case 
is the quality equal to the German stone. In Texas there is 
a stratum which is apparently a good quality of lithographic 
stone, but it is cut by joint planes, which prevent its extrac- 
tion in good-sized blocks. Below the surface this may be 
found to be less jointed, but the deposit has been scarcely 
prospected. Beds of this stone are also reported to occur in 
Virginia, Indiana, and Arkansas, but nothing can be said at 
present concerning their value. It seems very improbable 
that, among all the varieties of rock, of all ages and all 
kinds of origin, occurring in the west, this particular kind 
should be absent; and the most probable explanation of our 
non-production is ignorance of its character by the pros- 
pectors who have explored the region. 

Mica. 

The group of micas, which includes a great variety of 
minerals, all of which are complex silicates of alumina, with 



PRECIOUS STONES, ABRASIVE MATERIALS, ETC. 443 

varying proportions of iron, sodium, potassium, magnesium, 
etc., is one of the most common groups of minerals, being 
present in the greater number of metamorphic, many igneous, 
and some sedimentary rocks. It is, however, of value only 
when found in considerable quantities, in the form of large 
sheets ; and these occurrences are relatively rare. The two 
varieties, biotite and muscovite, are of commercial impor- 
tance, the former being only semi-transparent in thin sheets, 
while the latter is quite transparent. Large sheets of these 
minerals are found, usually in coarse pegmatite veins in 
granite, in coarse granite, and in thin beds in metamorphic 
rocks. 

Mica is obtained from several places in New Hampshire, but 
chiefly from the Palermo mine in Grafton County, which pro- 
duces nearly all the supply obtained in this country. Small 
quantities also come from North Carolina, and a very little 
from South Dakota and Wyoming. In the table at the close 
of this section it will be noticed that, since 1884, there has 
been a marked falling-off in the output of the country. This 
is due to the importation of a very fine grade of mica from 
India, where it occurs in extensive deposits which can be so 
easily worked and so cheaply produced that, even with a 
duty of 35 per cent ad valorem and the long distance of 
transportation, it can compete with the mica produced at 
home. 

Recently Canada has begun to produce mica in great 
quantities ; and the mineral, although biotite, and therefore 
not transparent, can be used for various purposes where trans- 
parency is not necessary. This biotite is obtained chiefly in 
Ottawa from the apatite mines, and the industry is succeed- 
ing that of apatite production which has been seriously 



444 ECONOMIC GEOLOGY OF THE UNITED STATES. 

checked by the important discoveries of phosphates in the 
United States. 

During the process of mining, the mica is obtained in as 
large pieces as possible ; and it is afterward cut into sheet 
mica, provided the quality is sufficiently good. For this 
purpose, either wine colour or white is desired, and the 
sheets must be smooth and free from spots. 

The price varies according to the size ; but of late years 
there has been an increasing demand for the smaller sizes, 
since the industry in which it is chiefly employed (panels 
of stove and furnace doors) now makes use of numerous 
small sheets instead of one large sheet. Sheet mica is 
also used extensively in electrical apparatus; and since 
colour is not important, the dark biotites of Canada are 
being used for this purpose. This class of mica must 
be flexible and non-conductive, and the sheets must be 
of uniform size, although many different sizes are made. 
There is also a rapidly increasing demand for ground 
mica, which is made of the scraps and waste produced 
in the manufacture of sheet mica. One of the most im- 
portant uses of this material is for the production of the 
frosted and spangled effect in wall papers, and the finer 
grades of ground mica are used for metallic white surfaces. 
Ground mica is also used in the manufacture of lubricants 
for car and carriage wheels. 

The production of mica in this country is shown in the 
following table. Of the output for 1892, New Hampshire 
produced, approximately, $70,000 ; North Carolina, $25,000 ; 
and the other $5000 was distributed between several states. 
The imports come chiefly from India and Canada. 



PRECIOUS STONES, ABRASIVE MATERIALS, ETC. 445 



PRODUCTION AND IMPORTS OF MICA IN THE UNITED 
STATES. 



Year. 


Pounds. 


Value. 


Imports. 


1880 


81,669 


$127,825 


$12,562 


1884 


147,410 


368,525 


27,555 


1890 


60,000 


75,000 


146,975 


1892 ...... 


75,000 


100,000 


100,846 



The waste and scrap material made into ground mica 
is not included in the above table. In 1892 it amounted 
to 959,000 pounds, valued at $67,130. 

Talc and Soapstone. 
A series of minerals of different varieties, but possessing 
the same general character, are included in this group. They 
are hydrated silicates of magnesia, and are soft, with a soapy 
feeling, a colour usually grayish or greenish, and a greasy 
lustre. Some, such as fibrous talc, bear a certain resemblance 
to asbestos ; and they are all characterized by their slight 
expansion during changes of temperature, which adapts 
them to certain particular uses. In an impure state they 
are common in metamorphic rocks, often in sufficient quan- 
tities to produce talcose schists ; and among these, beds of 
sufficient purity for commercial purposes are sometimes found. 
Nearly every state in the Union where metamorphic rocks 
occur has talc deposits ; but only a very few produce it. 
Steatite, or soapstone, is the most common form, and this is 
found in the metamorphic rocks of Pennsylvania, New Hamp- 
shire, New Jersey, Virginia, Vermont, and Maryland, but 



446 ECONOMIC GEOLOGY OF THE UNITED STATES. 

principally in the two first states. Fibrous talc is mined 
near Gouverneur, New York, but some comes also from 
Fairfax County, Virginia. 

Soapstone is obtained from quarries; and the large blocks 
are trimmed into slabs to be used for various purposes, such 
as hearths, mantels, fire-bricks, linings to stoves, laundry, 
bath, and acid tubs, etc. Aside from its slight expansion 
and contraction under changes of temperature, soapstone 
does not absorb acid or grease, and this makes it valuable 
for some of the above purposes. The smaller fragments are 
made into smaller articles, such as slate-pencils and orna- 
ments. Ground into a powder, it is used as an adulterant of 
soap, paper, rubber, etc. ; and owing to its extreme fineness 
of grain, it is valuable for paint, particularly that used for 
the protection of metal, since it not only adheres closely, but 
also resists the attacks of acids and solvents. Steatite grease 
is used as a lubricant, and there are many similar uses for 
the mineral. The aborigines quarried soapstone extensively 
for the manufacture of ornaments and pipes, these being 
easily fashioned because of the softness of the rock. 

The fibrous talc produced at Gouverneur, New York, is 
entirely ground to a powder, and used chiefly as a filler of 
medium quality paper and for increasing its weight. For 
the purpose of a filler, it is superior to clay, since it is fibrous 
and makes the paper stronger. It is also used as an adulter- 
ant of soap and of many white powdery substances. 

In 1889, 12,715 short tons of soapstone were produced 
in the United States, and of this 4371 tons came from 
Pennsylvania, 4250 tons from New Hampshire, 1500 tons 
from New Jersey, and 1 300 tons from Vermont. The pro- 
duction of talc and soapstone in the United States is shown 



PRECIOUS STONES, ABRASIVE MATERIALS, ETC. 447 

in the following table, in which it will be seen that the 
industry is a rapidly growing one : - — 

PRODUCTION OF TALC AND SOAPSTONE IN THE UNITED 

STATES. 





FlBROU 


s Talc. 


SOAPSTONE. 


Year. 


















Short Tons. 


Value. 


Short Tons. 


Value. 


1880 


4,210 


f57,730 


8,441 


$66,665 


1885 


10,000 


110,000 


10,000 


200,000 


1892 


51,000 


459,000 


19,000 


266,000 



Asbestos. 

There are two species of minerals which have a fibrous 
habit and marked resistance to heat, — one asbestos, a variety 
of hornblende, the other chrysotile, a variety of serpentine, 
and both called asbestos in the market. The first occurs 
in metamorphic rocks rich in the varieties of hornblende, the 
second is found in serpentines which have commonly resulted 
from the alteration of olivine-bearing rocks. Both are 
equally valuable for their power of resisting heat, but 
asbestos is inferior in strength and is not used where great 
strength is required. 

There are no deposits of chrysotile which are worked 
in this country, but asbestos is found in a belt of meta- 
morphic rocks on the eastern slope of the Appalachians 
from New York to Georgia. Limited amounts have been 
produced from here, but the principal source of asbestos 
in this country is California, although some occurs also in 
Wyoming. During 1891 this mineral was reported from 



448 ECONOMIC GEOLOGY OF THE UNITED STATES. 

several parts of the Cordilleras, and a company was organ- 
ized for its production in Gallatin County, Montana. 

The output of asbestos in this country has steadily 
decreased, and, in 1891, only 6Q tons, valued at $3960, 
were produced. Our supply comes almost entirely from 
Canada, which, since 1879, has become an important pro- 
ducer of chrysotile, the market having previously been 
supplied from Italy. The Italian asbestos has long fibres 
and is well suited to weaving. The Canadian chrysotile 
comes from the serpentine belt of the province of Quebec 
south of the St. Lawrence. Our imports of asbestos for 
1891 were valued at $358,461 ; and as these are rapidly 
increasing, it will be seen that the discovery of extensive 
deposits of this substance in this country is very desirable. 
In 1891 Canada produced 9279 short tons of asbestos, valued 
at $999,878. This mineral is used for fire-proof mineral 
cloth and paper, fire-proof paints, linings of fire-proof safes, 
for packing, for covering boilers, and for numerous purposes 
where fire-proof qualities are desired. 

Barite. 
This mineral, the sulphate of barium, also called barytes 
and heavy spar, is a common veinstone and is remarkable 
for its great weight. The chief commercial source in this 
country is from veins and pockets in limestones, principally 
from Missouri and Virginia, the work of extraction in the 
former state being done at intervals by farmers. Barite 
must be free from quartz-grains, which make the powder 
gritty, and from iron stains, which injure its normal white 
colour, although it may be made white by boiling in sulphuric 
acid and thus removing the iron stain. 



PRECIOUS STONES, ABRASIVE MATERIALS, ETC. 449 

Barytes is used as a pigment and as an adulterant for 
white lead, which it closely resembles in colour and weight, 
and for other purposes of adulteration. Its great weight 
and white colour make it valuable for these purposes, and 
it it said that it does not injure the quality of white lead. 
It is not distinctly injurious in other forms of adulteration. 
The United States produced, in 1891, 34,796 short tons of 
barite, valued at $ 118,363, and our imports of manufactured 
barium sulphate were valued at 122,458, and of the unman- 
ufactured barite, 18816. Of our output, in 1891, Missouri 
produced $60,000 worth; Virginia, $52,765; and the bal- 
ance, $5688 worth, came from North and South Carolina. 

Mineral Paints. 
Various mineral products, clays, minerals themselves, 
and compounds manufactured from them, are made use of 
in the manufacture of paint. Already chromium and cobalt 
ores have been considered, and, in the discussion of lead, 
it was stated that one of the most important uses of the 
metal was the production of white lead, which is of so 
much value in paint manufacture. In 1891 the white lead 
product was 78,018 short tons, valued at $10,454,029. The 
use of barite as an adulterant and the manufacture of zinc- 
white as a substitute for white lead have been referred to 
in previous pages. The value of the zinc-white produced 
in 1891 was $1,600,000. Red lead and litharge are also 
made artificially, the value of the red lead production in 1891 
being $591,730, and of litharge $720,925. Several metallic 
paints are also manufactured, and many colouring substances 
are made by chemical processes ; but the consideration of 
these scarcely comes within the scope of this work. 



450 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Natural metallic paint is made from the coloured clay 
which is sometimes produced by the decay of mineral veins, 
— copper producing green; iron, red and yellow earths, etc. 
Dark red and brown paints of this nature are mined in Penn- 
sylvania, New York, and elsewhere. In 1891, 25,142 short 
tons of such paint, valued at 1334,455, were produced. The 
production of ochre is also an important industry, and, even 
by the aborigines, clays coloured bright red and reddish 
yellow by iron peroxide were used as pigments. There are 
large deposits of such clays, and they are mined, finely 
ground, and then mixed in paints, giving both colour and 
body to them. In this industry Pennsylvania ranks first, 
but Virginia and Missouri also produce considerable quan- 
tities. During 1891 the output of 18,294 short tons of 
ochre was valued at $233,823. 

General Summary of Mineral Production. 

The mineral industry of the United States deserves to 
rank among the most important of our industries. In 1892 
approximately $670,000,000 worth of mineral products were 
won from the earth, this estimate for most of the minerals 
representing the value of the product at the mines. The 
materials thus won serve as the basis for a vast series of 
manufacturing industries and for a vast amount of exchange. 
In the industry of producing these materials, and in those 
industries which are dependent for existence upon the sup- 
plies of mineral products, a very considerable percentage of 
our population is employed. Indeed, it would be difficult 
to imagine the condition of the nation if these supplies 
were not at hand. 

Even more difficult is it to estimate the importance of 



PRECIOUS STONES, ABRASIVE MATERIALS, ETC. 451 

these mineral industries in aiding the growth of the nation 
and our remarkable industrial progress. There are two 
great primary industries, — the one supplying food and cer- 
tain products for manufacture, directly or indirectly from 
agricultural supplies ; the other, the extraction of substances 
from the earth and the manufacture of materials from them. 
In both of these industries the United States holds a high 
rank ; but, while there may be other nations which equal our 
agricultural industry, there are none which approach us in 
mineral resources. For the highest industrial development 
both of these industries should go hand in hand, and this is 
the case in the United States. 

While it may be said that industrial progress is largely 
dependent upon mineral resources, it is equally true that, for 
the highest development of these resources, a certain measure 
of progress in industry is first necessary, in the present state 
of our civilization. Thus it is that the mineral resources of 
the United States are, with the exception of certain precious 
and valuable metals and a few minor substances, developed 
chiefly in the eastern states. This is even more marked 
when the whole world is considered; for the industry of 
mineral production of Europe and the United States far 
exceeds that of all the rest of the world. This is partly due 
to lack of exploration, cost of transportation, sparseness of 
population, and other similar causes ; but it is also, in large 
part, due to the small degree of industrial progress. Why, for 
instance, do Mexico and the South American nations depend 
upon the European and American markets for so many 
products of the mineral industry? Certainly not for lack 
of opportunities. Japan has recognized this point and has 
undertaken to learn the lessons of industrial arts which 



452 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Europe and America have learned by centuries of experi- 
ence in their development. The people of the western part 
of our own country and the other nations of the American 
continents have reached the stage of production of crude 
materials for the use of those who know how to utilize 
them ; and the materials which are made from them are in 
part returned to the sections which produced the raw mate- 
rial. It is true that this is in a measure the result of sparse- 
ness of population, but only partly so. The southern states 
are rapidly emerging from this stage, and the west will find 
this its next step of progress. 

When this stage is reached, population increases more 
rapidly, and the demand for materials increases. Our east- 
ern states have reached the stage where nearly all economic 
minerals have a market value, and it is for this reason that 
these states hold so. high a rank in mineral production ; for 
the region is not rich in mineral resources, and only coal, 
iron, petroleum, building-stones, and minor substances are of 
importance. The west is the great mineral region of the 
country, and, indeed, of the world, but its resources are 
only partly developed. Iron, coal, building-stones, petroleum, 
salt, gypsum, and many minor substances are practically not 
produced in that section, although all of these are abundant. 
When this region is fully developed, it is doubtful if there 
will be any necessity of looking beyond the confines of the 
nation for more than a very few mineral products. Even at 
present the number of minerals which this country finds it 
necessary to import is small, and not only do we supply -our 
own needs, but we export more than we import of most min- 
eral products. Our total mineral exports are considerably 
in excess of the imports. 



PRECIOUS STOKES, ABRASIVE MATERIALS, ETC. 453 

The rank of the nation in metallic products is given at the 
close of Part II. ; but the statistics for non-metallic minerals 
are less valuable, since many of them are produced for local 
consumption rather than for exportation. In the production 
of petroleum, natural gas, and phosphates this country holds 
first rank, and it is doubtful if any nation has a greater pro- 
duction of building-stone. The rank of the country in the 
production of coal is second, and of salt third, among the 
nations of the world. 

The following table shows the value of the mineral pro- 
duction for materials whose total value, in 1892, exceeded 
$1,000,000: — 

VALUE OE MINERAL PRODUCTS OF THE UNITED STATES. 1 



Products. 



1880. 



1885. 



1890. 



1892. 



Pig iron (K T.) 

Bituminous coal 

Anthracite coal 

Silver (coining value) . . . 

Building-stone 

Lime 

Copper (N. T. value) . . . 
Gold (coining value) .... 

Petroleum 

Lead (N. T. value) .... 

Natural gas 

Zinc (N. Y. value) .... 

Cement 

Salt 

Mineral waters 

Phosphate rock 

Limestone for iron flux . . 

Zinc-white 

Mercury (San Francisco value) 
Potter's clay 



$101,466,500 
59,123,340 
38,680,250 
39,200,000 
18,356,055 
19,000,000 
11,491,200 
36,000,000 
24,1S3,233 
9,782,500 

2,277,432 
1,852,707 
4,829,566 

500,000 
1,123,823 
3,800,000 

763,738 
1,797,780 

200,457 



$64,712,400 

84,205,009 

76,698,000 

51,600,000 

19,000,000 

20,000,000 

18,292,999 

31,801,000 

19,198,243 

10,469,431 

4,857,200 

3,539,856 

3,492,500 

4,825,345 

1,312,845 

2,846,064 

1,678,478 

1,050,000 

979,189 

275,000 



$151,200,410 

108,708,000 

66,395,772 

70,485,714 

47,000,000 

35,000,000 

30,930,800 

32,845,000 

35,365,105 

14,266,703 

18,742,725 

7,474,962 

6,000,000 

4,752,286 

2,600,750 

3,213,795 

2,760,811 

1,600,000 

1,203,615 

756,000 



$136,806,915 

122,019,610 

74,624,614 

83,909,210 

45,000,000 

3S,500,000 

37,S50,000 

33,000,000 

30,229,128 

17,917,000 

13,000,000 

7,703,580 

6,586,098 

5,879,222 

3,000,000 

2,361,219 

2,097,600 

1,200,000 

1,119,720 

1,000,000 



1 Extracted from Both well's Mineral Industry, 1892, pp. 4- 



454 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



As will be seen, there has been a considerable change in 
the rank of importance of the various industries since 1880. 

The following table shows the total value of the mineral 
products of the country at intervals during the past thirteen 
years. This is exclusive of brick clays and some minor 
products which are not considered in this treatise. 

TOTAL VALUE OF THE MINERAL PRODUCTS OF THE 
UNITED STATES. • 





Metallic 


Nok-Metallic 


Total 




Products. 


Products. 




1880 . . . 


$201,283,094 


$165,440,966 


$366,724,060 


1882 . 






219,860,518 


223,408,023 


443,268,541 


1884 . 






186,468,162 


212,697,759 


399,165,921 


1886 . 






215,658,334 


247,208,210 


462,866,544 


1888 . 






256,623,933 


299,988,780 


556,612,713 


1890 . 






308,641,957 


337,696,669 


646,338,626 


1892 . 






318,638,596 


350,959,283 


669,597,879 



For the ten years ending 1889, the total mineral product 
of the United States amounted to 84,627,343,630, of which 
less than one-half, or 82,165,000,310 worth, were metallic 
products. In the above table it will be noticed that, while 
there has been a marked increase in the output of both 
metallic and non-metallic products, the most striking in- 
crease has been in the last-named group ; and this will 
probably be more marked in the next decade. 

The following table, prepared from materials in the 
Eleventh Census, shows the value of the mineral industries 
in the fourteen states which had an output of over $10,000,000 



PRECIOUS STONES, ABRASIVE MATERIALS, ETC. 455 



in 1889. In the case of each state the principal mineral 
products are given in the order of their importance, based 
upon their value, but the products of minor importance are 
not listed although they are included in the total valuation. 
Thus in Pennsylvania the most important product is coal, 
the second petroleum, the third natural gas, etc. For each 
industry the rank which the state holds, in comparison with 
the other states, is also given in figures : — 

MINERAL PRODUCTION OF LEADING STATES, 1889. 



States. 


Value. 


Most Important Mineral Products. 


Pennsylvania . 


$150,876,649 


11 11 
Coal, petrole am, 1 natural gas, stone, 


3 

iron ore. 


Michigan . . 


70,880,524 


1 2 1 

Iron ore, copper, salt. 




Colorado . . 


41,126,610 


1 2 7 1 12 
Silver, gold, coal, lead, stone. 




Montana . . 


33,737,775 


1 2 4 

Copper, silver, gold. 




Ohio. . . . 


26,653,439 


3 2 2 3 

Coal, stone, petroleum, natural gas. 




New York . . 


24,165,206 


3 1 2 2 

Stone, cement, iron ore, salt. 




California . . 


19,699,354 


2 9 8 1 

Gold, stone, silver, mercury. 




Illinois . . . 


17,110,317 


2 8 

Coal, stone. 




Missouri . . 


15,931,575 


8 7 12 

Coal, stone, zinc ore, lead. 




Utah . . . 


11,681,019 


3 3 

Silver, lead. 




Minnesota . . 


11,542,138 


Iron ore, stone. 




Iowa . . . 


10,267,068 


Coal. 




Wisconsin . . 


10,183,861 


Iron ore, stone. 




Nevada . . . 


10,143,878 


4 3 

Silver, gold. 





In 1889, of the total output of the country, which 
amounted to 1587,230,662, 1386,616,834 worth came from 

1 Including the New York output. 



456 



ECONOMIC GEOLOGY OF THE UNITED STATES. 



states east of the Mississippi, and $252,083,744 worth, or 
nearly one-half of the total, came from those states east of 
the Mississippi which are partly in the Appalachians or 
which border the Atlantic. This is not so strikingly shown 
in the above table as it would have been had the states of 
minor importance (with an output of less than $10,000,000) 
been included in the table. 

The value of the imports and exports of the leading 
products is shown in the following table. Aside from these, 
the exports and imports amount to only a few million dollars 
annually. 

EXPORTS AND IMPORTS OF MINERAL PRODUCTS, 1891. 



Minerals. 


Exports. 


Imports. 


Gold coin and bullion 

Silver coin and bullion 

Silver ore 

Petroleum 


$79,086,581 

27,692,879 

1,592,931 

46,174,835 

30,736,442 

15,703,543 

3,000,0001 
130,371 

173,887 


$44,970,110 

18,192,750 

9,724,716 


Iron, and steel, and their products . . 

Tin and terne plate 

Block tin 


41,983,626 

25,900,305 

8,091,363 


Copper 


1,665,729 


Precious stones 


12,745,435 


Coal 


1,800,000! 


Cement 


4,411,330 
2,867,633 
2,675,192 


Lead 

Sulphur 






Total 


$204,291,469 


$175,028,189 





In this table some manufactured articles are also included. 
If manufactured tin and the precious stones were omitted, 
our exports would greatly exceed our imports of mineral 
products. 



1 Estimated. 



APPENDIX. 



LITERATURE OF ECONOMIC GEOLOGY. 

This list does not pretend to be a bibliography, nor is 
there even an attempt to refer to all of the many valuable 
general treatises upon the various aspects of economic 
geology. With the exception of works upon mining methods 
and metallurgy, these references are usually to works with 
which the author is personally familiar. For special descrip- 
tions of localities and individual economic products of this 
country, the files of the American Journal of Science and 
the Engineering and Mining Journal are of particular value, 
and in these there are many hundred articles of this nature. 
Similar sources in other countries may be resorted to for 
accounts of the mineral products abroad ; and there, as well 
as in this country, such descriptions are also found scattered 
through the geological literature. There is no complete 
bibliography of the subject. 1 

The national geological survey reports of the various 
countries all contain something of economic geology, and 
such descriptions usually possess great scientific as well as 
practical value. In the United States very important de- 

1 Since the above was written an extremely valuable treatise, entitled Ore 
Deposits of the United States, by J. F. Kemp, has been published, and one 
of the most important parts of the work is its very complete and extensive 
bibliography. 

457 



458 ECONOMIC GEOLOGY OF THE UNITED STATES. 

scriptions of the local mineral resources are found in the 
various state geological survey reports. Nearly every state 
in the Union has at one time or another supported a geo- 
logical survey, and at present many states still have such 
surveys. In these, full description of the local economic 
geology will be found. Thus the Pennsylvania reports 
contain very complete descriptions and statistics concerning 
the coal, oil, gas, and iron industries of the state, the 
Ohio reports contain the same with reference to that state ; 
the New Jersey geological survey publishes valuable infor- 
mation concerning the clays and iron mines ; and many 
other states publish similar reports. These surveys, when 
in their best development and when properly managed, keep 
in advance of the development of the state, and show 
where valuable deposits exist and how they may be obtained. 
Thus the clay industry of New Jersey is the direct outcome 
of the work of the geological survey, the bauxite deposits 
of Arkansas were discovered by the survey of that state, and 
the oil and coal industries of several states owe much to the 
work of the state geologists and their assistants. Usually 
the publications of the surveys merely describe the local 
deposits ; but one state, Arkansas, has gone farther than this 
and treated the subject in hand from a broader standpoint. 
Thus this state publishes monographs upon manganese and 
novaculites, which not only describe the local deposits, but 
show the position of these products in general and the 
probable future of the local industries. This is vastly more 
valuable than the mere record of local observations and 
of local development. 

In the following list of books of reference, individual 
mention of the special articles in the magazines and the 



APPENDIX. 459 

geological reports is not made, excepting in exceptional 
cases where the material is of unusual value. Nor is 
especial effort made to include European works excepting 
such English and a few continental treatises as are of 
general interest. 

TEXT-BOOKS OF MINERALOGY AND GEOLOGY. 

Dana, System of Mineralogy, 1892. 

Dana, Text-Book of Mineralogy. 

Dana, Manual of Mineralogy and Lithology. 

Bauerman, Descriptive Mineralogy. 

Bauerman, Systematic Mineralogy. 

Brush, Determinative Mineralogy and Blowpipe. 

Nason, Manual of Qualitative Blowpipe Analysis. 

Williams, Crystallography. 

Rosenbusch, Microscopical Physiography of the Rock-Making Minerals 

(translated by Iddings). 
Rosenbusch, Mikroskopische Physiographic der Massigen Gesteine. 
Rutley, The Study of Rocks. 

Yon Cotta, Rocks Classified and Described (translated by Lawrence). 
Le Conte, Elements of Geology. 
Dana, Manual of Geology. 
Prestwich, Physical and Chemical Geology. 
Jukes-Browne, Physical Geology. 
Lyell, Principles of Geology. 
Geikie, Class-Book of Geology. 
Gelkie, Text-Book of Geology, 1893. 

GENERAL TREATISES UPON ECONOMIC GEOLOGY. 

Phillips, Ore Deposits, 1884. 

Whitney, Metallic Wealth of the United States. 

Whitney, The United States. 

Davies, A Treatise on Metalliferous Minerals and Mining, 1892. 

Da vies, Earthy and Other Minerals and Mining, 1888. 

Kemp, Ore Deposits of the United States, 1893. 



460 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Lakes, Geology of Colorado and Western Ore Deposits, 1893. 
Osborn, Minerals, Mines, and Mining, 1888. 
Page, Economic Geology. 
Ansted, The Applications of Geology. 
Williams, Applied Geology, 1886. 
Belt, Mineral Veins. 

Von Cotta, A Treatise on Ore Deposits (translated by Prime). 
Yon Cotta, Die Lehre von der Erzlagerstatten. 
Von Groddeck, Die Lehre von den Lagerstatten der Erze. 
Sandberger, Untersuchungen uber Erzgange. 
Grimm, Die Lagerstatten der Nutzbaren Mineralien. 
Serlo-Lattner, Bergbankunde. 
Bur at, Mineraux Utiles. 

Rothwell, The Mineral Industry, etc., of the United States, for 1892. 
Reports of the Tenth and Eleventh Census on Mineral Industries, etc. 
Annual Reports upon the Mineral Resources of the United States (Day, 
U.S. Geol. Survey). 

SPECIAL ARTICLES. 

Pumpelly, Johnson's Cyclopaedia, 1886, VI., p. 22 (article on Ore 

Deposits). 
Newberry, Deposition of Ores {Columbia School of Mines Quarterly, 

1880, Vol. V., p. 337). 
Le Conte, Genesis of Metalliferous Veins {American Journal of Science, 

1883, Vol. XXVI., pp. 1-19). 
Raymond, Mining Statistics for 1870, p. 448. 
Kemp, The Filling of Mineral Veins {Columbia School of Mines' Quarterly, 

No. 1, XIII.). 
Wads worth, State Board of Geological Survey for 1891-92, p. 144. 

WORKS UPON SPECIAL SUBJECTS. 

Iron. 

Pumpelly, Tenth Census, Vol. XV., pp. 1-601. 
Eleventh Census volume on Mineral Industries. 

Pumpelly, Geological Survey of Missouri, Report for 1872, Part I. 
Winchell (N. H. and H. V.), The Iron Ores of Minnesota, Bull. 6, 
Minn. Geol. Survev, 1891. 



APPENDIX. 461 

Irving and Van Hise, The Penokee Iron-bearing Series of Michigan and 
Wisconsin, Tenth Annual Report U.S. Geol. Survey, pp. 347-458. 

Summary Final Report, Second Geol. Survey of Pennsylvania, Vols. 1. 
and II., (also forthcoming volumes). Also scattered reports in Penn- 
sylvania survey publications. 

Kendall, The Iron Ores of Great Britain, 1893. 

Gold, Silver, and Lead. 

Lock, Gold, its Occurrence and Extraction. 

Whitney, The Auriferous Gravels. 

Smyth, The Gold Fields of Victoria. 

Annual Reports of the Director of the Mint (for Gold and Silver). 

Williams, Popular Fallacies regarding the Precious Metal Ore Deposits 

(Fourth Annual Report U.S. Geol. Survey, pp. 257-267). 
Lord, Comstock Mines and Mining, Monograph IV., U.S. Geol. Survey, 

1883. 
Becker, Geology of the Comstock Lode, Monograph III., U.S. Geol. Survey, 

1882. (Also, in abstract, Second Annual Report U.S. Geol. Survey, 

pp. 293-325.) 
Emmons, Geology and Mining Industry of Leadville, Colorado, Monograph 

XII., U.S. Geol. Survey. (Also, in abstract, Second Annual Report 

U.S. Geol. Survey, pp. 203-287.) 
Curtis, The Silver-Lead Deposits of the Eureka Mining District, Nevada, 

Monograph VII., U.S. Geol. Survey, 1884. (Also, in abstract, Fourth 

Annual Report U.S. Geol. Survey, pp. 225-251.) 

Zinc, Copper, Mercury, Manganese, Tin, and Aluminum. 

Chamberlain, Geology of Wisconsin, 1873-1879, Vol. IV., pp. 367-571. 

(Zinc.) 
Irving, The Copper-bearing Rocks of Lake Superior, Third Annual Report 

U.S. Geol. Survey, pp. 89-188. (Copper.) 
Pumpelly, Geological Survey of Michigan, 1869-1873, Vol. L, Part IT. 

(Copper.) 
Becker, Geology of the Quicksilver Deposits of the Pacific Coast, Monograph 

XIII., U.S. Geol. Survey, 1888. (Also Eighth Annual Report U.S. 

Geol. Survey, pp. 965-985.) (Mercury.) 
Eleventh Census volume on Mineral Industries, pp. 202-245. (Mercury.) 



462 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Le Conte and Rising, The Phenomena of Metalliferous Vein-formation 

now in Progress at Sulphur Bank, California (American Journal oj 

Science, XXIV., 1882, pp. 23-33). (Mercury.) 
Le Conte, On Mineral Vein-formation now in Progress at Steamboat 

Springs, etc. (American Journal of Science, XXV., 1883, pp. 424-428). 

(Mercury.) 
Penrose, Manganese, Annual Report Arkansas Geol. Survey, Vol. L, 

1890. (Manganese.) 
Rothwell, Mineral Industry, etc., for 1892, pp. 439-462. (Tin.) 
Eleventh Census volume on Mineral Industries, pp. 247-265 (Tin.) 
Richards, Aluminum, its Properties, Metallurgy, and Alloys, 1890. 

(Aluminum.) 
Eleventh Census, Mineral Industries, pp. 277-284. (Aluminum.) 
Mineral Resources of the United States, 1891, pp. 147-163. (Aluminum.) 
Rothwell, Mineral Industry, etc., of the United States for 1892, pp. 

11-18. (Aluminum.) 

Coal. 
Leavitt, Facts about Peat. 
Shaler, General Account of the Fresh Water Morasses of the United States, 

Tenth Annual Report U.S. Geol. Survey, pp. 261-338. 
Willis, The Lignites of the Great Sioux Reservation, Bull. 21, U.S. Geol. 

Survey, 1885. 
Dumble, The Lignites of Texas, Texas Geol. Survey, special report. 
Hayden Reports — Geol. Survey of the Territories. 
Smyth, A Rudimentary Treatise on Coal and Coal Mining. 
MacFarlane, Coal Regions of America. 
Lesley, Manual of Coal and its Topography, 1856. 
Lesquereux, On the Vegetable Origin of Coal. Annual Report Second 

Geol. Survey of Pennsylvania, 1885, pp. 95-124. 
Lesley, Forthcoming report Pennsylvania Geol. Survey, Summary Final 

Report, Vol. III. 
Hull, The Coal Fields of Great Britain. 
White, Comparative Stratigraphy of the Bituminous Coal Field of the 

Northern Half of the Appalachian Field, Bull. 65, U.S. Geol. Survey, 

1891. 
Eleventh Census volume on Mineral Industries, pp. 343-422. 
Mineral Resources, 1891 (Day, U.S. Geol. Survey), pp. 177-402. 
Pennsylvania Geological Survey Reports, particularly Reports A A and AC. 



APPENDIX. 463 

Petroleum. 
Crew, A Practical Treatise on Petroleum. 
Orton, The Trenton Limestone as a Source of Oil and Natural Gas in Ohio 

and Indiana, Eighth Annual Report U.S. Geol. Survey, 1889, pp. 

475-662. 
Tenth Census Report, Vol. X., pp. 1-319. 
Eleventh Census Report on Mineral Industries, pp. 425-591. 
White, The Mannington Oil Field, Bull. Geol. Society America, Vol. 3, 

1892, pp. 187-216. 
Lesley, Summary Final Report Pennsylvania Geol. Survey, Vol. II., 

1892. 
Pennsylvania Geological Survey Reports, particularly I 5, III and Annual 

Report, 1886, Part II (the latter containing a complete bibliography 

of Petroleum). 
Ohio Geological Survey Reports. 

Building-Stones, etc. 

Merrill, Stones for Building and Decoration, 1891. 

Hull, A Treatise on Building and Ornamental Stone of Great Britain and 

Foreign Countries. 
Burnham, Limestone and Marble, 1883. 
Tenth Census volume on Building-Stones. 
Eleventh Census volume on Mineral Industries, pp. 595-666. 
Smock, Building- Stone in New York, Bull. New York State Museum, 

1888. 
Shaler, Geology of Cape A nn, Massachusetts, Ninth Annual Report, 

U.S. Geol. Survey, pp. 529-611. (Granite.) 
Harris, Granites and our Granite Industries. 
Da vies, A Treatise on Slate and Slate Quarrying. 
Rothwell's Mineral Industry, etc., pp. 49-56. (Cement.) 
Mineral Resources of the United States for 1891, pp. 529-538. (Cement.) 

Soils, Clays, Fertilizers, etc. 

Shaler, The Origin and Nature of Soils, Twelfth Annual Report U.S. 

Geol. Survey, 1892, pp. 213-345. (Soils.) 
Johnson and Cameron, Elements of Agricultural Chemistry and Geology. 
Hill, Mineral Resources of the United States for 1891, pp. 474-528. 

(Clays.) 



464 ECONOMIC GEOLOGY OF THE UNITED STATES. 

Penrose, The Nature and Origin of Phosphate of Lime, Bull. 46, U.S. 

Geol. Survey. (Fertilizers.) 
Hill, The Occurrence of Artesian and other Underground Waters in 

Texas, etc. (Agricultural Dept.). (Artesian Wells.) 
Chamberlain, The Requisite and Qualifying Conditions of Artesian Wells, 

Fifth Annual Report U.S. Geol. Survey, pp. 125-173. 
Peale, Eleventh Census, volume on Mineral Industries, pp. 779-787. 

(Mineral Waters.) 

Miscellaneous Minerals. 

Streeter, Precious Stones and Gems, 1892. 

Kunz, Gems and Precious Stones, 1892. 

Griswold, Whetstones and Novaculites of Arkansas, Annual Report 

Arkansas Geological Survey for 1890, Vol. III. 
Chatard, Salt-Making Processes in the United States, Seventh Annual 

Report U.S. Geol. Survey, pp. 497-527. 
Jones, Asbestos, its Properties and Occurrence, 1890. 

MINERAL STATISTICS. 

Rothwell, The Mineral Industry, etc., of the United States for 1892. 
Day, Mineral Resources of the United States (Annual Report issued by 

the U.S. Geol. Survey). Also earlier volumes edited by Williams, 

etc. 
Tenth Census Reports upon Mineral Products. 
Eleventh Census volume on Mineral Industries. 
Production of Gold and Silver in the United States (Annual Report 

Director of the Mint). 
Taylor (revised by Holdeman), Statistics of Coal. 

MINING METHODS. 

Davies, A Treatise on Metalliferous Minerals and Mining, 1892, pp. 314- 

490. 
Greenwell, Mine Engineering, 1889. 
Balch, The Mines, Miners, and Mining Interests of the United States in 

1882. 
Hunt, British Mining, 1884. 
Michell, Mine Drainage, 1881. 
Abel, Mining Accidents and their Prevention, 1889. 



APPENDIX. 465 

Kunhardt, The Practice of Ore Dressing in Europe, 1884. 
Lock, Mining and Ore Dressing Machinery, 1890. 
Andre, A Treatise on Mining Machinery, 1877. 
Bowie, A Practical Treatise on Hydraulic Mining, 1885. 
Whitney, Auriferous Gravels. 
Hughes, A Text-Book of Coal Mining, 1892. 
Andre, A Practical Treatise on Coal Mining, 1879. 
Pamely, The Colliery Manager's Handbook, 1891. 
Walton, Coal Mining Described and Illustrated. 
Booth, Marble Workers' Manual. 

ALLOYS AND METALLURGY. 

Brannt, Metallic Alloys, 1889. 

Hiorns, Mixed Metals, 1890. 

Bauerman (revision of Phillips), Elements of Metallurgy, 1891. 

Phillips, Elements of Metallurgy, 1874. 

Roberts- Austen, A n Introduction to the Study of Metallurgy, 1892. 

Overman, Treatise on Metallurgy. 

Bloxam, Metals, their Properties and Treatment. 

Makins, A Manual of Metallurgy. 

Mitchell, A Manual of Practical Assaying. 

Ricketts, Notes on Assaying. 

Hiorns, Practical Metallurgy and Assaying, 1888. 

Howe, The Metallurgy of Steel, 1891. 

Greenwood, Steel and Iron. 

Bauerman, The Metallurgy of Iron. 

Osborn, The Metallurgy of Iron and Steel. 

Gore, The Art of Electro-Metallurgy. 

Eissler, The Metallurgy of Gold. 

Eissler, The Metallurgy of Silver. 

Eissler, The Metallurgy of Argentiferous Lead. 

Hofman, The Metallurgy of Lead, 1893. 

Howe, Copper Smelting, Bull. 26. U.S. Geol. Survey. 



EKE ATA. 

On p. 152, twelfth line from bottom of page, for "his" read "this." 
On p. 441, tenth line from bottom of page, for "inorganic" read 
organic." 



LIST OF AUTHORS AND WORKS REFERRED 
TO IN THE TEXT. 



PAGE8 

Adams, F. D., Canadian Record of Science, 1891, pp. 463-469 35 

Becker, G. F., Monograph U.S. Geological Survey, III., 1882 185, 187 

Becker, G. F., Monograph U.S. Geological Survey, XIII., 1888 254, 255 

Brannt, W. T., Metallic Alloys 171 

Brooks (T. B.) and Pompelly (R.), Geological Survey of 

Michigan, 1869-73 124 

Brush, G. J., Blowpipe Analysis 27 

Burnham, S. M., Limestone and Marble 359 

Carll, J. F., Annual Report Pennsylvania Geological Survey, 

1886, Part II., pp. 830-895 337 

Carll, J. F., Pennsylvania Geological Survey, Report III., 

pp. 270-284 340 

Chamberlain, T. C, Fifth Annual Report U.S. Geological 

Survey, pp. 125-173 412 

Clayton, J. E., Engineering and Mining Journal, Vol. 45, 

1888, p. 108 191 

Curtis, J. S., Monograph U.S. Geological Survey, VII., 1884 . 187 

Dana, E. S., Manual of Mineralogy 3, 27 

Dana, E. S., System of Mineralogy 3, 27 

Dana, E. S., Text-Book of Mineralogy 3,27 

Dana, J. D., Manual of Geology 51 

Da vies, D. C, Earthy and Other Minerals and Mining . . . 199 

Da vies, D. C, Metalliferous Minerals and Mining 80, 96, 199 

Dumble, E. T., Brown Coal and Lignite of Texas . . . . . 319 
Eleventh Census volume on Mineral Industries . . 138, 151, 155, 176, 274, 

283, 312, 337, 366, 383, 421 

Emmons, S. F., Monograph U.S. Geological Survey, XIL, 1886 80, 234 

Fairbanks, H. W., American Geologist, 1891, VII., pp. 209-222 152 

467 



468 LIST OF AUTHORS AND WORKS. 

PAGES 

Foster (J. W.) and Whitney (J. D.), Keport on the Geology 

of the Lake Superior Land District, Part II., 1851 . . . 124 

Geikie, A., Class-Book of Geology 51 

Geikie, A., Text-Book of Geology 51, 80 

Griswold, L. S., Annual Keport Arkansas Geological Survey, 

1890,111 429 

Groddeck, A. von, Die Lehre von dem Lagerstdtten der Erze . 199 
Hill, R. T., Mineral Resources of the United States (Day, 

U.S. Geological Survey) for 1891, pp. 474-528 .... 399 
Hill, R. T., The Occurrence of Artesian and Other Under- 
ground Waters in Texas, etc. (Agricultural Dept.), 1892 . 412 

Hiorns, A. H., Mixed Metals 171 

Iddings, J. P., translator of Rosenbusch's Microscopical 

Physiography 4 

Irving (R. D.) and Van Hise (C. R.), Tenth Annual Report 

U.S. Geological Survey, pp. 341-508 124, 125 

Jukes-Browne, A. J., Physical Geology 51 

Kemp, J. F., Ore Deposits of the United States 80, 457 

Kunz, G. F., Gems and Precious Stones of North America . . 421 
Le Conte, J., American Journal of Science, XXV., 1883, 

pp. 424-428 255 

Le Conte, J., American Journal of Science, XXVI., 1883, 

pp. 1-19 80, 255 

Le Conte, J., Elements of Geology 51, 80 

Le Conte (J.) and Rising (W. B.), American Journal of 

Science, XXIV., 1882, pp. 23-33 255 

Lesley, P., Pennsylvania Geological Survey, Summary Final 

Report, Vol. 1 131 

Lesquereux, L., Pennsylvania Geological Survey, 1885, 

pp. 95-124 322 

Lord, E., Monograph U.S. Geological Survey, IV., 1883 . . 182 

Merrill, G. P., Stones for Building and Decoration, 1891 . . 359, 383 
Mineral Resources of the United States (Day, U.S. Geological 

Survey), 1891 283, 287, 312, 337, 383, 387, 421 

Newberry, J. S., School of Mines Quarterly, 1880 80 

Newell, F. H., Eleventh Census Bulletin, No. 193 ... . 418 

Ohio Geological Survey Reports 337 

Orton, E., Eighth Annual Report U.S. Geological Survey, 

1889, pp. 475-662 337 



LIST OF AUTHORS AND WORKS. 469 

PAGES 

Peale, A. C, Eleventh Census Report on Mineral Industries, 

pp. 779-787 418 

Pennsylvania Geological Survey Reports 337 

Penrose, R. A. F., Jr., Annual Report Arkansas Geological 

Survey, 1890, Vol. 1 262 

Penrose, R. A. F., Jr., Bulletin 46, U.S. Geological Survey . 405 

Penrose, R. A. F., Jr., Journal of Geology, Vol. I., pp. 275-282 266 

Phillips, J. A., Ore Deposits 80, 191, 199, 255, 274 

Pumpelly, R., Johnson's Cyclopaedia 80 

Pumpelly, R., Geological Survey of Missouri for *1872, 

Parti 126 

Pumpelly (R.) and Brooks (T. B.), Geological Survey of 

Michigan, 1869-1873 124 

Raymond, R. TV, Mining Statistics, 1870 80 

Richards, J. W., Aluminum, its Properties, Metallurgy, and 

Alloys, 1890 283 

Rising (W. B.) and Le Conte (J.), American Journal of 

Science, XXIV., 1882, pp. 23-33 255 

Rosenbusch, H., Microscopical Physiography, translated by 

J. P. Iddings 4 

Rosenbusch, H., Mikroskopische Physiographic der Massigen 

Gesteine 34 

Rothwell, R. P., The Mineral Industry, etc., of the United 

States for 1892 140, 151, 257, 274, 283, 335, 337, 387, 453 

Russell, I. C, American Journal of Science, XLIIL, 1892, 

p. 178 328 

Russell, I. C, Journal of Geology, Vol. I., 1893, p. 233 ... 328 

Russell, I. C, National Geographic Society Magazine, III., 

1891, pp. 53-204 328 

Sandberger, F., Untersuchungen iiber Erzgange 73, 86 

Shaler, N. S., Twelfth Annual Report U.S. Geological Sur- 
vey, pp. 213-345 391 

Siver, L. D., Engineering and Mining Journal, Vol. 45, 1888, 

pp. 195-196, 212 189 

Streeter, E. W., Precious Stones and Gems 421 

Tenth Census, Vol. X 337, 359 

Tenth Census, Vol. XV 119 

Van Hise (C. R.) and Irving (R. D.), Tenth Annual 

Report U.S. Geological Survey, pp. 341-508 .."..... 124, 125 



470 LIST OF AUTHORS AND WORKS. 

PAGES 

Wadsworth, M. E., Catalogue of the Michigan Mining- 
School, 1892 79 

Wadsworth, M. E., Report of the Michigan State Board of 

Geological Survey 79, 80 

White, I. C, Bulletin Geological Society of America, Vol. 3, 

1892, pp. 187-216 344 

AVhitney, J. D., Auriferous Gravels 155 

Whitney, J. D., Metallic Wealth of the United States ... 80, 155 

Whitney, J. D., The United States 155 

Whitney (J. D./ and Foster (J. W.), Report on the Geology 

of the Lake Superior Land District, Part II., 1851 . . . 124 

Williams, G. H., Elements of Crystallography 3 

Winchell, N. H. and II. V., Bulletin No. 6, Minnesota 

Geological Survey, 1891 126 



INDEX. 



Abrasive materials, 425. 

production of United States, 429. 
Acid springs, 419. 
Adirondack magnetite mines, 142. 
Adit level, 106, 107. 
iEolian soils, 395. 
Africa, copper in, 219, 220. 

copper production of, 226, 227. 

gold in, 165. 

gold production of, 174, 175. 

iron ores of, 135. 

natural soda in, 437. 
Agate, use of, in jewelry, 423. 
Agatized wood, production of United 

States, 424. 
Aix la Chapelle, zinc deposits, 245. 
Alabama, bauxite in, 285. 

bauxite production of, 291. 

coal in, 315. 

coal production of, 317, 333, 334. 

iron in, 121. 

iron production of, 138, 139, 144, 
145, 307. 

limestone production of, 379. 

phosphates in, 407. 

tin in, 275. 
Alaska, coal in, 320. 

gold fields of, 160. 

gold production of, 161, 173. 
Alaskan coal district, 313, 319. 
Albertite, 355. 

Algoma, Canada, copper mines, 220. 
Alkali, 434. 
Alkaline saline springs, 419. 

springs, 419. 
Alloys of aluminum, 289. 
antimony, 297. 
copper, 222. 



Alloys of gold, 171. 
iron, 136. 
lead, 239. 
manganese, '270. 
nickel, 294. 
silver, 201. 
tin, 282. 
treatises on, 465. 
Almaden, Spain, mercury mine, 255, 

256. 
Almeria, Spain, lead district, 236. 
Altai Mountains, gold in, 164. 
Aluminum, 283. 
alloys of, 289. 
bronze, 289. 
cost of, 287. 
history of, 284, 286. 
metallurgy of, 286, 287. 
mineralogical association of, 284. 
occurrence of, 283. 
ores of, 25. 
production of, 290. 
France, 291. 
Germany, 290. 
Switzerland, 291. 
United States, 290. 
properties of, 288. 
treatises on, 462. 
uses of, 288.. 
Alumnite, 284. 
Amalgamation, 113, 114. 
of gold, 113. 
silver, 113. 
American copper mines, 221. 
Amherst, Ohio, buff sandstone, 370. 

blue sandstone, 370. 
Amorphous structure, 2. 
Amphibole minerals in the rocks, 7. 
Amygdules, 83, 211. 
Analyses of anthracite, 312. 



471 



472 



INDEX. 



Analyses of bituminous coal, 312. 
cements, 388, 389. 
coal, 312. 

hydraulic cement, 388, 389. 
lignite, 312. 
peat, 312. 
phosphates, 409. 
Portland cement, 388, 389. 
natural gas, 350. 
Ancient river gravels, 154. 
Andreasberg, Germany, mining dis- 
trict, 198, 218, 236. 
Anglesite, 22, 228. 
Anhydrous sesquioxide of iron, 119. 
Annabergite, 14, 292. 
Anthracite, 311. 
analyses of, 312. 
occurrence of, Colorado, 319. 
New Mexico, 311, 319. 
Pennsylvania, 315, 316. 
Rhode Island, 311, 314. 
production of Appalachian field, 
321. 
New England field, 321. 
Pennsylvania, 316, 333. 
Rocky Mountain field, 321. 
United States, 331, 453. 
Anticline, 50. 
Anticlinal Theory for accumulation of 

petroleum, 344. 
Antimony, 296. 
alloys of, 297. 

occurrence of, Arkansas, 297. 
California, 297. 
Nevada, 297. 
foreign, 297. 
ores of, 26. 
price of, 298. 

production of, Austria-Hungary, 
298. 
Canada, 298. 
Italy, 298. 
Japan, 298. 
Nevada, 307. 
Spain, 298. 

United States, 298, 304, 305. 
the world, 298, 299. 
uses of, 297. 
Apatite, 12, 405. 



Apatite, distribution of, 405. 

occurrence of, Canada, 406. 

origin of, 406. 
Appalachian Mountains, asbestos in, 
447. 

building-stones in, 384, 385. 

coal district of, 313, 315. 

coal production of, 321. 

economic products of, 60. 

formation of, 68. 

general characters of, 59. 

gold fields of, 147, 148. 

lead in, 229. 

manganese in, 264. 

ore deposits, absence of, 95. 

silver veins in, 192. 
Appalachian states, copper in, 209. 

lead production of, 240. 

slate in, 374. 
Archean, division of, 66. 

land areas, 65. 

rocks, origin of, 40. 
Arctic, climate of, 328, 329. 
Argentiferous blende, 180. 

chalcopyrite, 180. 

galena, 21, 180, 181, 228. 
Argentine Republic, guano in, 407. 
Argentite, 21, 80. 
Argillaceous hematite, 19. 
Aroa, Venezuela, copper mine, 218. 
Arizona, copper in, 209. 

copper production of, 224, 225, 
307. 

gold production of, 173. 

lead in, 235. 

lead production of, 240, 241. 

onyx in, 382. 

silver in, 191. 

silver production of, 204. 
Arizona Copper Mine, 216. 
Arkansas, antimony in, 297. 

bauxite in, 286. 

lithographic stone in, 442. 

manganese in, 263, 265. 

manganese, production of, 271, 307. 

novaculites in, 428. 

zinc production of, 251. 
Arkansas oilstones, 428. 
Artesian wells, 412. 






INDEX. 



473 



Artesian wells, association with syn- 
clines, 415. 
cause of, 413. 

conditions for existence, 414. 
in arid regions, 416. 
California, 418. 
Colorado, 418. 
South Dakota,' 418. 
Texas, 418. 
United States, 418. 
Utah, 418. 
similarity of petroleum wells to, 

343. 
treatises on, 464. 
value of, 416. 

in the United States, 418. 
Asbestos, 14, 447. 
distribution of, 447. 
imports of, 448. 
occurrence of, 447. 
production of, Canada, 448. 
treatises on, 464. 
uses of, 448. 
Ashio, Japan, copper mine, 218, 220. 
Asia, copper production of, 226, 227. 
iron ores of, 135. 

natural soda, occurrence in, 437. 
Asia Minor, borax in, 435. 

chromium in, 300. 
Aspen, Colorado, silver mines, 189. 
Asphalt, 356. 
Asphaltum, 340, 355. 
distribution of, 356. 
imports of, 357. 

occurrence of, California, 356, 357. 
Kentucky, 356. 
Sicily, 356. 
Texas, 356. 
Trinidad, 356, 357. 
Utah, 356. 
origin of, 356. 

production of United States, 357. 
uses of, 357. 
Atalla, Alabama, hematite, 123. 
Augite as a rock-forming mineral, 8, 

10. 
Auriferous gravels, California, 153. 
origin of, 155. 
Victoria, 162. 



Auriferous quartz, origin of, 169. 
Australia, gold coinage, 172. 

iron ores of, 135. 

copper production of, 226. 

manganese in, 267. 

silver in, 199. 

tin in, 280. 

tin production of, 283. 
Australasia, copper in, 219. 

copper production of, 226. 

gold in, 161. 

gold production of, 163, 174, 175. 

silver in, 197. 

silver production of, 206. 
Austria, bauxite in, 285. 

copper in, 208, 219. 

gold in, 165. 

iron ores of, 134. 

mercury in, 256. 

mercury production of, 261, 262. 

spelter production of, 252. 

tin production of, 283. 

zinc production of, 252. 
Austria-Hungary, antimony produc- 
tion of, 298. 

chromium in, 300. 

coal production of, 335. 

gold production of, 175. 

lead in, 237. 

lead production of, 242. 

nickel-cobalt in, 293. 

ozokerite in, 357, 358. 

silver in, 198, 199. 

silver production of, 198, 206. 

zinc in, 237, 246. 
Azurite, 22, 208. 

in Russia, 219. 

B. 

Babbitt metal, 297. 

Ballarat, Victoria, gold district, 161. 

Banca tin deposits, 279. 

Banded structure in mineral veins, 

85, 98, 99. 
Barite, 17, 448. 

production of Missouri, 449. 
North Carolina, 449. 
South Carolina, 449. 



474 



INDEX. 



Barite production of United States, 
449. 
Virginia, 449. 
uses of, 449. 
Barometers, use of mercury in, 260. 
Barrier Range, Australia, silver dis- 
trict, 197. 
Barytes, 448. 

Basic secretions in granite, 362. 
Batesville, Arkansas, manganese de- 
posits, 265. 
Baux, France, bauxite occurrence, 

285. 
Bauxite, 25, 284, 285. 
occurrence of, 285, 303. 
Alabama, 285. 
Arkansas, 286. 
Austria, 285. 
Cordilleras, 285. 
France, 285. 
Georgia, 285. 
Germany, 285. 
Italy, 285. 
production of Alabama, 291. 
France, 291. 
Georgia, 291. 
Belgium, coal production of, 335. 
iron ores of, 134. 
lead in, 237. 
phosphates in, 410. 
phosphate production of, 411. 
spelter production of, 252. 
zinc in, 237, 245. 
zinc production of, 252. 
Bell metal, 222. 
Benzine, 341, 347. 
Berea grit, 355. 

Ohio, grit, 370, 427. 
Bichromate of potash, 299. 
Big Bone Salt Lick, Kentucky, 410. 
Bilboa, Spain, iron deposits, 134. 
Billeton, tin deposits, 279. 
Biotite, 8, 443. 

Birmingham, Alabama, iron produc- 
tion, 141. 
Bitumen, 356. 
Bituminous coal, 311. 
analyses of, 312. 
in Appalachian Mountains, 317. 



Bituminous coal production of Penn- 
sylvania, 333. 
United States, 331, 453. 
Blackband, 119, 132. 
Black copper mine, Arizona, 216. 
Black Forest, Germany, zinc deposits, 

246. 
Black Hills, South Dakota, gold in, 
158, 168. 
silver in, 192. 
tin mines of, 275. 
Black Jack, 23. 
Blende, 23, 228, 243. 

argentiferous, 180. 
Blind-seams in granite, 365. 
Blue Ridge, tin in, 275. 
Bluestone, 371, 372. 
distribution of, 385. 
occurrence of, 385. 
production of New Jersey, 373. 
New York, 373, 
Pennsylvania, 373. 
United States, 373, 386. 
Bog iron ore, 19, 119, 135. 
in New England, 121. 
precipitation of, 82. 
Bog manganese, 24. 
Boleo, Mexico, copper mine, 220. 

production of, 226. 
Bolivia, copper in, 218. 
gold production of, 166. 
silver in, 195. 

silver production of, 196, 206. 
tin in, 280. 

tin production of, 283. 
Bonanza, 184. 
Bonanza mines, 159. 
Bone beds, 405. 
Borax, 434. 

occurrence of, Asia Minor, 435. 
California, 435. 
Chili, 435. 
Cordilleras, 435. 
Nevada, 435. 
Thibet, 435. 
Tuscany, 435. 
origin of, 435. 
price of, 436. 
production of California, 436. 



INDEX. 



475 



Borax production of Nevada, 436. 
United States, 436. 
uses of, 436. 
Borneo, mercury in, 257. 

mercury production of, 261. 
platinum in, 177. 
Bornite, 208. 
Bort, 425. 
Bosses, 37. 
Branch-veins, 102. 

Brandon, Vermont, limonite deposits, 
122. 
manganese deposits, 264. 
Brass, 223, 249. 
Braunite, 262. 
Brazil, gold production of, 166. 

platinum in, 177. 
Breccia, 29, 100. 
Brick clays, 400, 401. 
Brines, 430. 

British Columbia, platinum in, 177. 
British Guiana, gold production of, 

175. 
Britannia metal, 282, 297. 
Brittany, France, tin deposits, 278. 
Bromine, 434. 

occurrence of, Michigan, 434. 

West Virginia, 434. 
production of United States, 434. 
Bronze, 222, 282. 
Brown hematite, 19, 119, 120. 
method of mining, 122. 
occurrence of, 121, 302. 
Alabama, 121. 
Georgia, 121. 
Pennsylvania, 121. 
Texas, 121. 
Virginia, 121. 
production of, 120. 
Alabama, 139, 144. 
-Colorado, 143. 
Georgia, 144. 
Michigan, 139, 144. 
Missouri, 143. 
Pennsylvania, 141, 144. 
Tennessee, 143. 
Virginia, 142, 144. 
Wisconsin, 143. 
Brown stone, 370. 



Brusa, Asia Minor, chromite deposits, 

300. 
Buddie, 112. 
Buhr, French, 427. 
Buhrstone, 427. 

production of United States, 429. 
Building-stones, 359. 
distribution of, 384. 
occurrence of, 384. 
production of California, 383, 384, 
386, 455. 
Colorado, 383, 384, 386, 455. 
Connecticut, 383, 384, 386. 
Illinois, 383, 384, 386, 455. 
Indiana, 383, 384, 386. 
Maine, 383, 384, 386. 
Massachusetts, 383, 384, 386. 
Minnesota, 383, 384, 386, 455. 
Missouri, 383, 384, 386, 455. 
New Jersey, 383, 384, 386. 
New York, 383, 384, 386, 455. 
Ohio, 383, 386, 455. 
Pennsylvania, 383, 386, 455. 
United States, 383, 385, 386, 

453. 
Vermont, 383, 384, 386. 
Wisconsin, 383, 384, 386, 455. 
treatises on, 463. 
Burden, New York, iron mine, 132, 

142. 
Burmah, tin in, 280. 
Butte, Montana, copper mines, 214, 
220. 
silver mines, 190. 



C. 



Calamine, 23, 243. 

Calcining ores, 114. 

Calcite as a rock-forming mineral, 

9, 10. 
Calcium sulphide, 438. 
California, antimony in, 297. 
artesian wells in, 418. 

asbestos in, 447. 

asphaltum in, 356, 357. 

auriferous gravels, 153. 

borax in, 435. 

borax production of, 436. 



476 



INDEX. 



California, building-stone production 
of, 383, 384, 386, 455. 

chromium in, 299. 

chromium production of, 307. 

copper in, 216. 

copper production of, 224, 307. 

diamonds in, 423. 

gold fields, development of, 150. 

gold production of, 173, 307, 455. 

granite production of, 368. 

grindstones in, 427. 

gypsum production of, 405. 

infusorial earth in, 426. 

lead production of, 240. 

limestone production of, 379. 

magnesite in, 437. 

manganese in, 266. 

manganese production of, 271. 

marble in, 381. 

marble production of, 383. 

mercury in, 253. 

mercury production of, 255, 307, 
455. 

metal production of, 305. 

mineral products of, 455. 

mineral water production of, 420. 

natural gas in, 351. 

onyx in, 382. 

petroleum in, 337, 338, 340. 

petroleum production of, 348. 

platinum in, 176. 

quartz gold mines of, 148. 

salt in, 433. 

sandstone in, 372. 

silver in, 191. 

silver production of, 204, 455. 

slate in, 374. 

tin in, 276. 
Calumet and Hecla, Michigan, copper 
mine production of, 210, 
213. 
Cambrian land areas, 67. 
Canada, antimony production of, 298. 

apatite deposits in, 406. 

asbestos in, 448. 

asbestos production of, 448. 

copper in, 220. 

gold in, 167. 

gold production of, 167, 175. 



Canada, iron ores of, 135. 
iron pyrite in, 301. 
iron pyrite production of, 301. 
lead production of, 242. 
manganese in, 266. 
manganese production of, 272. 
mica in, 443, 444. 
nickel in, 293. 
nickel production of, 296. 
natural gas production of, 355. 
petroleum in, 338, 340. 
petroleum production of, 349. 
phosphate production of, 411. 
platinum in, 177. 
platinum production of, 178. 
salt production of, 434. 
silver in, 193, 194. 
Cape Ann, Massachusetts, granite in, 

365. 
Cape of Good Hope, copper produc- 
tion of, 227. 
Carbon group of minerals, 11. 
Carbonas, 278. 
Carbonate of iron, 119. 
occurrence of, 135, 302. 
production of, 132. 
Ohio, 144. 
Pennsylvania, 141. 
Carbonic acid, during Carboniferous 

period, 330. 
Carboniferous period, carbonic acid 
in, 330. 
climate of, 327. 
coal, 313. 

conditions existing in, 325, 326. 
moisture in, 328. 
submergence of land during, 

326. 
vegetation of, 325, 327. 
Caret, 171. 
Carrara, Italy, marble imports from, 

382. 
Carrizal, Chili, copper mine, 217. 

manganese deposits, 267. 
Cartersville, Georgia, manganese dis- 
trict, 264. 
Caspian region, petroleum in, 338, 

340. 
Cassiterite, 25, 274. 



INDEX. 



477 



Castner process of sodium production, 

287. 
Catlinite, production, United States, 

424. 
Caucasus Mountains, gold in, 164. 

manganese in, 267. 
Cave opening, 230, 232. 
Cavern theory for the accumulation 

of petroleum, 344. 
Cavities, origin of, 75. 

of minor importance, 78. 

resulting from faulting, 77. 

resulting from solution, 77. 
Cement, 359, 387. 

analyses of, 388, 389. 

exports of, 456. 

imports of, 390, 456. 

production of, New York, 455. 

United States, 389, 453. 

Central America, silver in, 193, 194. 

silver production of, 206. 
Central coal area, 313, 318. 

production of, 321. 
Central plains, disturbance in, 62. 

economic products of, 62. 

general features of, 61. 
Central states, building-stones in, 
385. 

sandstone in, 369. 
Cerargyrite, 21. 
Cerro de Pasco, Peru, silver mines, 

196, 258. 
Cerrusite, 23. 228. 
Ceylon, graphite in, 441. 
Chalcocite, 22, 208. 
Chalcopyrite, 22, 180, 208. 
Chamber deposits, 80, 84. 
Chanarcillo, Chili, silver mines, 197. 
Chateaugay, New York, iron mines, 

129. 
Chemical ore deposits, 80, 82. 
Chemically precipitated rocks, 30. 
Chert, 125. 

Chester, Massachusetts, emery de- 
posits, 427. 
Child's Valley, California, magnesite 

deposits, 437. 
Chili, borax in, 435. 

cobalt in, 294. 



Chili, cobalt production of, 296. 

copper in, 209, 217, 220. 

copper production of, 226, 227. 

gold production of, 166, 167, 175. 

guano exports of, 407. 

manganese in, 267. 

manganese production of, 272. 

phosphate production of, 411. 

silver in, 197. 

silver production of, 197, 206. 
China, gold in, 166. 

gold production of, 174. 

iron ores of, 135. 

natural gas in, 352. 
Chincha Islands, Peru, guano de- 
posits, 406. 
Chlorite, origin of, 9. 
Chrome green, 299. 
Chrome iron, 177. 
Chrome steel, 299. 
Chrome yellow, 299. 
Chromite, 14, 299. 
Chromium, occurrence of, 299. 
foreign, 300. 
United States, 299. 

origin of, 299. 

production of, California, 307. 
United States, 300, 304, 305. 

uses of, 299. 
Chrysocolla, 22, 208. 
Chrysotile, 15, 447. 

occurrence of, Canada, 448. 
Cinnabar, 24, 253, 260. 
Clastic, definition of, 28. 
Clay iron stone, 19. 
Clay rocks, 29. 
Clays, 359, 399. 

distribution of, 401. 

occurrence of, 401. 

treatises on, 463. 

uses of, 400, 401. 
Clay selvage, 99. 
Claystone, 29. 

Clausthal district, Germany, 198, 236. 
Cleavage, definition of, 6. 

slaty, 373, 374. 
Clifton copper district, Arizona, 215. 
Climate in Carboniferous period, 327. 
Clinton, New York, red hematite, 123. 



478 



INDEX. 



Clinton ore bed, extent of, 123. 

origin of, 123, 124. 
Coal, 311. 

analyses of, 312. 
Appalachian district, 314, 315. 
areas in the United States, 313. 
as a part of the earth's crust, 11. 
association with iron, 317. 
consumption of in United States, 

331. 
discovery of in United States, 315. 
distribution of, 312. 
exports of, 331, 456. 
future of, 332. 
imports of, 331, 456. 
occurrence of, Alabama, 315. 

Alaska, 313, 319, 320. 

Central Area, 313, 318. 

Colorado, 319. 

Europe, 312, 320. 

foreign, 320. 

Georgia, 315. 

Kentucky, 315. 

Maryland, 315. 

Northern Area, 313, 318. 

Nova Scotia, 314. 

Ohio, 315. 

Pacific Coast Area, 313, 319. 

Pennsylvania, 315. 

Rhode Island, 314. 

Rocky Mountain Area, 313, 
319. 

Tennessee, 315. 

Texas, 318. 

United States, 312. 

Virginia, 315. 

Washington, 320. 

Western Area, 313, 318. 

West Virginia, 315. 
origin of, 32, 311, 321-326. 
price of, 334. 

production of, Alabama, 317, 333, 
334. 

Appalachian field, 321. 

Austria- Hungary, 335. 

Belgium, 335. 

Central field, 321. 

Colorado, 333, 334, 455. 

Prance, 335. 



Coal production of Germany, 335. 
Great Britain, 335, 336. 
Illinois, 333, 334, 455. 
Indiana, 333. 
Indian Territory, 334. 
Iowa, 333, 455. 
Kansas, 334. 
Kentucky, 333. 
Maryland, 333. 
Missouri, 333, 455. 
New England field, 321. 
Northern field, 321. 
Ohio, 333, 334, 455. 
Pacific Coast field, 321. 
Pennsylvania, 333, 334, 455. 
Rocky Mountain field, 321. 
Russia, 335. 
Spain, 335. 
Tennessee, 334. 
United States, 321, 331, 333, 

334, 335, 336, 453. 
Washington, 334. 
Western field, 321. 
West Virginia, 317, 333. 
World, 335. 
treatises on, 462. 
uses of, 331. 
Coastal plains, 52. 
Coast Range, period of formation of, 

69. 
Cobalt, 292. 
blue, 295. 
minerals, 13, 26. 
occurrence of, 294, 303. 
Chili, 294. 

New Caledonia, 293, 294. 
Norway, 293. 
Pennsylvania, 293. 
Sweden, 293. 
origin of, 294. 
production of, Chili, 296. 
New Caledonia, 296. 
Prussia, 296. 

United States, 296, 304, 305. 
uses of, 295. 
Cobaltite, 14. 
Cceur d'Alene, Idaho, silver-lead 

mines, 191, 235, 240. 
Coke, 332. 



INDEX. 



479 



Cologne, Germany, zinc deposits, 

236, 246. 
Coinage gold, character of, 171. 
Coinage of gold, 172. 

platinum, 177. 

silver, 201, 204. 
Colombia, gold production of, 166, 
174. 

platinum in, 177. 

platinum production of, 178. 

salt production of, 434. 

silver in, 197. 

silver production of, 206. 
Colorado, anthracite in, 319. 

artesian wells in, 418. 

brown hematite in, 143. 

building-stone production of, 383, 
384, 386, 455. 

coal in, 319. 

coal production of, 333, 334, 455. 

copper in, 216. 

copper production of, 224, 307. 

gold in, 158. 

gold production of, 173, 307, 455. 

granite production of, 368. 

iron production of, 139, 143. 

lead in, 233. 

lead production of, 240, 241, 307, 
455. 

manganese production of, 271, 
272. 

metal production of, 305. 

mineral production of, 455. 

mineral water production of, 420. 

nickel in, 292. 

petroleum in, 337, 338, 339. 

petroleum production of, 348. 

sandstone production of, 371, 372. 

silver in, 181, 189. 

silver production of, 204, 205, 
307, 455. 
Columnar hematite, 19. 
Comb structure, 98, 99. 
Comstock Lode, 181. 

bonanzas in, 184. 

galleries in, 108. 

heat in, 108, 184. 

history of, 182. 

occurrence of ore, 185. 



Comstock Lode, origin of ore, 186. 

production of, 159, 184, 205. 
Concentrated contact ore deposits, 

80, 93. 
Concentration of ores, 103, 110. 
Concretionary action, 89. 

ore deposits, 80, 89. 
Conglomerate, 29. 

Connecticut, building-stone produc- 
tion of, 383, 384, 386. 
granite production of, 368. 
limestone production of, 380. 
nickel in, 292. 
sandstone in, 369. 
sandstone production, 371. 
Contact ore deposits, 80, 92. 

metamorphism, 92. 
Copper, 208. 
alloys of, 222. 

consumption in United States, 224. 
distribution of, 220. 
exports, 456. 
imports, 225, 456. 
mineralogical association of, 208, 

221. 
native, 22. 

occurrence of, 208, 221, 302. 
Africa, 219, 220. 
Appalachian States, 209. 
Arizona, 209, 215. 
Australasia, 219. 
Austria, 208, 219. 
Bolivia, 218. 
California, 216. 
Canada, 220. 
Chili, 209, 217, 220. 
Colorado, 216. 
England, 208, 219. 
Germany, 208, 218, 220. 
Italy, 219. 
Japan, 218, 220. 
Mexico, 220. 
Michigan, 209. 
Montana, 209, 214. 
Newfoundland, 220. 
New Mexico, 216. 
Norway, 219. 
Peru, 218. 
Portugal, 216, 220. 



480 



INDEX. 



Copper, occurrence of, Eussia, 219. 

Spain, 209, 216, 220. 

Sweden, 219. 

United States, 209. 

Utah, 216. 

Venezuela, 217. 

Vermont, 209. 
ores of, 22. 
origin of, 220, 222. 
price of, 224, 227. 
production of, 224. 

Africa, 226, 227. 

Arizona, 224, 225, 307. 

Asia, 226, 227. 

Australasia, 226. 

California, 224, 307. 

Chili, 226, 227. 

Colorado, 224, 307. 

Europe, 226, 227. 

Germany, 226, 227. 

Japan, 226, 227. 

Lake Superior district, 210. 

Maine, 225. 

Mexico, 226. 

Michigan, 224, 225, 307, 455. 

Montana, 215, 224, 225, 307, 
455. 

New Hampshire, 225. 

New Mexico, 224. 

North America, 226, 227. 

Portugal, 226, 227.- 

Eussia, 226. 

South America, 226, 227. 

Spain, 226, 227. 

United States, 224, 225, 226, 
227, 304, 305, 453. 

Utah, 224. 

Venezuela, 226, 227. 

Vermont, 225. 

World, 226, 227. 
Copper pyrites, 22. 
Copper Queen mine, Arizona, 216. 
Copper, treatises on, 461. 

uses of, 222, 223. 
Copperfield, Vermont, copper mine, 

209. 
Coquina, 376. 

Cordilleran region, economic re- 
sources of, 64. 



Cordilleran region, general features 

of, 63. 
Cordilleras, abundance of metals in, 
95, 306. 

as a source of lead, 228. 

bauxite in, 285. 

borax in, 435. 

building-stone in, 384, 385. 

dessicated lakes in, 64. 

gold fields of, 158. 

gypsum in, 404. 

marble in, 381. 

salt in, 430, 432. 

silver in, 181. 

tin in, 275. 

zinc in, 243. 
Cornwall, England, copper of, 219. 

influence of rock on veins, 102. 

lead mines of, 237. 

silver occurrence of, 199. 

stockwerks in, 89. 

tin mines of, 277, 278, 280, 281. 
Cornwall, Pennsylvania, iron mines, 

131, 138, 140. 
Coronado, Arizona, copper mines, 

215. 
Corundum, 13, 25, 284, 425, 427. 

production of United States, 429. 
Corundum Hill, North Carolina, cor- 
undum of, 427. 

sapphire of, 423. 
Country rock, 98, 99. 
Course, 100. 
Cradle, 111. 

Creede, Colorado, silver mines, 189. 
Cretaceous coals, 314, 318, 319, 320. 
Cretaceous coastal plains, 55. 

economic products of, 56. 
Cretaceous land areas, 69. 
Crimora, Virginia, manganese district, 

264. 
Cross-cuts, 105, 106. 
Cross-section, 101. 
Cryolite, 25, 284, 440. 
Crystalline structure, 2. 
Cuba, manganese in, 266. 

manganese production of, 272. 
Cuprite, 22. 
Cut-off plane in granite, 365, 366. 



INDEX. 



481 



D. 

Dakota, gold production of, 173, 307. 
Dalmatia, California, gold mines, 152. 
Dannemora, Sweden, magnetite of, 

134. 
Davis, Massachusetts, iron pyrite 

mines, 301. 
Davy, experiments on aluminum, 286. 
Delaware, granite production of, 368. 
Delta soils, 395. 
Dendrites, 24. 
Developing veins, 105. 
Deville process of extracting alumi- 
num, 286. 
Devonshire, England, copper in, 219. 

lead in, 237. 

silver in, 199. 

tin in, 278. 
Diabase, use as granite, 367. 
Diamonds, character of, 12. 

occurrence of, California, 423. 
Georgia, 423. 
Montana, 422. 
North Carolina, 423. 

production of, United States, 424. 

use for abrasive purposes, 425. 
Diaspore, 284. 
Diatomaceous earth, 32. 
Diatoms, 426. 
Dickerson, New Jersey, iron mine, 

143. 
Dikes, 37. 

Diorite, use as granite, 367. 
Dip, 51, 100. 
Dip-fault, 51. 

Disintegration of rocks, 391, 392. 
Disseminated eruptive ore deposits, 

80. 
Divider, 88. 
Dolomite, 10, 247. 
Douglas Island, Alaska, gold deposits, 

160. 
Downthrow of fault, 50. 
Drainage of mine, 106. 
Dressing of ores, 103. 
Drifts, 107. 
Drive, 106. 
Droppers, 102. 
Durango, Mexico, tin in, 281. 



E. 

Eastern Archean Mountains, eco- 
nomic products of, 59. 

general characters of, 58. 
Eastern states, spelter production of, 
250. 

zinc production of, 250. 
Economic geology, treatises on, 459. 
Effusive rocks, 36. 
Ekaterinoslav, Russia, mercury in, 

257. 
Elaterite, 355. 

Electrolytic process of extracting alu- 
minum, 286, 287. 
Elements, combinations of, 3. 

composing the earth's crust, 1. 

metals and metalloids, 3. 

native, 1. 
Emery, 425, 427. 

imports of, 427. 

occurrence in Georgia, 427. 
Massachusetts, 427. 
North Carolina, 427. 

production of United States, 429. 
England, copper in, 208, 219. 

lead in, 237. 

tin in, 277. 
Eruptive ore deposits, 80. 
Eruptive rocks, geological age of, 

42. 
Erzgebirge, Germany, tin in, 278. 
Estuary theory for origin of coal, 

323. 
Eureka district, Nevada, 187. 
Europe, coal in, 312, 320. 

copper production of, 226, 227. 

manganese in, 267. 

silver in, 197, 199. 

zinc in, 247. 
Exports of cement, 456. 

coal, 331, 456. 

copper, 456. 

gold, 456. 

iron, 145, 456. 

lead, 456. 

mineral products, 456. 

petroleum, 456. 

silver, 456. 
Extrusive rocks, 36. 



482 



INDEX. 



F. 

Fault, 50. 

Fault breccia, 29, 77. 

Faults, effect of on veins, 101. 

Feeders, 102. 

Feldspar in the rocks, 6, 10. 

production of United States, 401, 
402. 

use of for pottery, 401. 
Ferro-manganese, 270. 
Fertilizers, kinds of, 402. 

phosphatic, 405. 

treatises on, 464. 
Fibrous talc, 445. 

occurrence in United States, 446. 
Findlay, Ohio, gas region, 352. 
Finland, gold in, 164. 

tin in, 279. 
Fire clays, 400, 401. 
Fissure veins, 80, 84. 
Flags, 373. 

Flat openings, 230, 232. 
Flats, 231. 

Flaxseed iron ore, 20, 123. 
Flint, concretions of, 89. 

production of in United States, 
402. 

use for pottery, 401, 402. 
Flood plain soils, 395. 
Florence, Colorado, petroleum field, 

339. 
Florida, phosphates in, 407, 408. 

phosphate production of, 409. 

plains, 54. 
Fluccan, 98, 99. 
Fluorite, 17, 440. 
Flux, use of, 114. 

use of limestone for, 378, 379, 380. 
Foot wall, 99, 106. 
Forest of Dean, Great Britain, iron 

mines of, 133. 
Forest on Malaspina glacier, Alaska, 

328, 329. 
Fossil hematite ore, 20, 119, 123. 
Fragmental, definition of, 28. 

rocks, origin of, 31. 
Frame, 112. 
France, aluminum production of, 291. 

bauxite in, 285. 



France, bauxite production of, 291. 

coal production of, 335. 

lead in, 237, 238. 

manganese in, 267. 

phosphate in, 410. 

manganese in, 267. 

silver in, 198. 

silver production of, 206. 

tin in, 278. 
Franklin Furnace, New Jersey, zinc 

deposit, 20, 114, 244, 263. 
Franklinite, 20, 23, 243. 
Fredonia, New York, gas wells, 351. 
Free coinage of silver, 202. 
Freestone, 370. 

Freiberg, district Germany, 198, 236. 
French buhr, 427. 

French Guiana, phosphate production 
of, 411. 



G. 



Galena, 22, 180, 181, 228. 

Galena limestone, 229. 

Galenite, 22. 

Galicia, Austria, ozokerite in, 357. 

Gangue, 17, 97. 

Garnets, 423. 

production of United States, 424. 
Garnierite, 292, 294. 
Gash veins, 80, 84, 230, 232. 

in Mississippi valley, 84. 
Gasoline, 347. 
Gems, imports of, 425. 
Geodes, 83. 
Geographical zones in the United 

States, 52. 
Geological association of ore deposits, 
94. 

history of the United States, 65. 

map, 100. 

surveys ; state and national, 457. 

text-books, 459. 
Georgia, bauxite in, 285. 

bauxite production of, 291. 

brown hematite in, 121. 

brown hematite production of, 144. 

coal in, 315. 

diamonds in, 423. 



INDEX. 



483 



Georgia, gold in, 148. 

granite production of, 368. 

iron production of, 139, 143. 

manganese in, 263, 264. 

manganese production of, 271, 307. 

marble in, 381. 

marble production of, 383. 

red hematite production of, 143. 
Germany, aluminum production of, 
290. 

bauxite in, 285. 

coal production of, 335. 

copper in, 208, 218, 220. 

copper production of, 226, 227. 

gold coinage of, 172. 

gold in, 165. 

iron ores of, 134. 

iron pyrite production of, 301. 

lead in, 236. 

lead production of, 242. 

lithographic stone in, 442. 

manganese in, 268. 

mercury in, 257. 

nickel production of, 296. 

petroleum production of, 349. 

salt production of, 434. 

silver in, 197, 199, 294, 295. 

silver production of, 198, 206. 

tin in, 278. 

tin production of, 283. 

zinc in, 236, 245, 246. 
Germany and Luxemburg, iron pro- 
duction of, 146. 
Gibbsite, 284. 
Gilsonite, 355, 356. 
Glacial clays, 400. 

Glacial period, economic effects of, 70. 
Glacial soils, 396, 397. 
Glaciation during Pleistocene, 70. 
Glassy structure, 2. 
Glens Falls, New York, marble, 381. 
Globe copper district, Arizona, 216. 
Globigerina ooze, 31. 
Gneiss, characters of, 39. 

use as granite, 366. 
Gogebic, Wisconsin, iron range, 140, 

143. 
Golconda, Nevada, manganese de- 
posit, 266, 270. 



Gold, 20. 

alloys of, 171. 

bearing conglomerates in Aus- 
tralia, 168. 

origin of, 168. 
bearing gravels, 154. 

origin of, 155. • 
bearing sandstone, Black Hills, 
168. 

quartz, origin of, 169. 
circulation of, 167. 
coinage, 171, 172. 

amount of, 172. 
conditions of accumulation, 147. 
effect of weathering upon, 103. 
exports of, 456. 

extraction by amalgamation, 113. 
fields of California, development 
of, 150. 

early history of, 149. 
fields of the Cordilleras, 158. 
foil, 249. 

foreign regions, 161. 
future of, 159. 
imports of, 456. 
occurrence of, 168, 303. 

Africa, 165. 

Alaska, 160. 

Altai Mountains, 164. 

Appalachian Mountains, 147. 

Australasia, 161. 

Austria, 165. 

California, 148. 

Canada, 167. 

Caucasus Mountains, 164. 

China, 166. 

Colorado, 158. 

Finland, 164. 

Georgia, 148. 

Germany, 165. 

Hungary, 165. 

India, 166. 

Japan, 166. 

Mexico, 167. 

Montana, 158. 

Nevada, 159. 

New South Wales, 162. 

New Zealand, 162. 

North Carolina, 148. 



484 



INDEX. 



Gold, occurrence of, Nova Scotia, 168. 

Queensland, 162. 

Eussia, 163. 

Siberia, 163. 

South Africa, 164. 

South America, 166. 

South Carolina, 148. 

South Dakota, 158. 

Tasmania, 163. 

Transvaal, 164. 

Urals, 163. 

Victoria, 161. 

Yukon valley, 160. 
origin of, 168. 
production of, 171. 

Africa, 174, 175. 

Alaska, 161, 173. 

Appalachian field, 148. 

Arizona, 173. 

Australasia, 163, 174, 175. 

Austria-Hungary, 175. 

Bolivia, 166. 

Brazil, 166. 

British Guiana, 175. 

California, 173, 307, 455. 

Canada, 167, 175. 
. Chili, 166, 167, 175. 

China, 174. 

Colorado, 173, 307, 455. 

Colombia, 166, 174. 

Dakota, 173, 307. 

Idaho, 173. 

India, 166, 174. 

Mexico, 175. 

Montana, 173, 307, 455. 

Nevada, 173, 307, 455. 

New Mexico, 173. 

New South Wales, 162. 

New Zealand, 162. 

Oregon, 173. 

Peru, 166, 167. 

Queensland, 162. 

Russia, 164, 174, 175. 

South Africa, 165. 

South Carolina, 173. 

United States, 173, 174, 175, 
304, 305, 453. 

Utah, 173. 

Venezuela, 175. 



Gold production of Victoria, 161. 

World, 174, 175, 203. 
quartz production of, United 

States, 424. 
segregation of, 170. 
segregation veins of, 152. 
source of, 147. 
treatises on, 461. 
uses of, 170. 
washing, 155. 
Gossan, 98. 
Gothite, 19, 119. 
Gouge, 99. 
Gouverneur, New York, fibrous talc 

deposits, 446. 
Grahamite, 355. 
Granite, 360. 

blind seams in, 365. 
blotches in, 362. 
characters of, 360, 361. 
colour of, 361. 
distribution of, 384. 
durability of, 362. 
green seams in, 365. 
joint planes in, 363, 364, 365. 
occurrence of, 361. 
production of, California, 368. 

Colorado, 368. 

Connecticut, 368. 

Delaware, 368. 

Georgia, 368. 

Maine, 368. 

Maryland, 368. 

Massachusetts, 368. 

Missouri, 368. 

New England States, 368. 

New Hampshire, 368. 

New Jersey, 368. 

New York, 368. 

Pennsylvania, 368. 

Rhode Island, 368. 

South Dakota, 368. 

United States, 368. 

Vermont, 368. 

Virginia, S68. 

Wisconsin, 368. 
rift in, 363, 365, 366. 
sap in, 363. 
stones sold as, 366. 



INDEX. 



485 



Granite, texture of, 361. 

uses of, 361, 367. 

weathering of, 363. 
Graphite, 11, 311, 441. 

imports of, 441. 

production of, United States, 441. 
Graphitic anthracite, Rhode Island, 

311, 314, 441. 
Great Basin, natural soda in, 437. 

origin of, 64. 
Great Bonanza of Comstock Lode, 

185. 
Great Britain, coal production of, 
335, 336. 

gold coinage of, 172. 

iron in, 133. 

iron production of, 146. 

iron pyrite production of, 301. 

lead in, 237. 

lead production of, 242, 243. 

manganese in, 267. 

manganese production of, 272. 

nickel production of, 296. 

nickel-cobalt in, 293. 

phosphate production of, 411. 

salt production of, 434. 

silver coinage of, 204. 

silver in, 199. 

spelter production of, 252. 

tin production of, 283. 

zinc in, 237, 246. 

zinc production of, 252. 
Great Salt Lake, salt from, 430. 
Greece, chromite in, 300. 
Greenland, native iron in, 81, 119. 
Green seams in granite, 365. 
Grindstones, 425, 427. 

occurrence of, California, 427. 
Michigan, 427. 
Ohio, 427. 
South Dakota, 427. 

production of, United States, 429. 
Ground mica, 444. 
Ground plan, 101. 

Guadalajara, Spain, silver mines, 198. 
Guadalcazar, mercury mines, 258. 
Guanajuata, Mexico, silver deposits, 

193. 
Guano, 405. 



Guano exports from Chili, 407. 

occurrence in Argentine Republic, 
407. 

South America, 406. 

Uruguay, 407. 
Gypsum, 13, 359. 

association of, with salt, 404, 431, 

432. 
imports of, 405. 
occurrence of, 403. 

in Cordilleras, 404. 
origin of, 404. 
production of, California, 405. 

Iowa, 405. 

Kansas, 405. 

Michigan, 405. 

New York, 405. 

Ohio, 405. 

South Dakota, 405. 

United States, 405. 

Utah, 405. 

Virginia, 405. 
use as a fertilizer, 402, 403. 
use in jewelry, 423. 



H. 

Hade, 50, 100. 

Hanging wall, 99, 106. 

Harney's Peak, South Dakota, tin 
mines, 276. 

Harz Mountains, manganese mines, 
268, 270. 

Heat in Comstock Lode, 184. 

Heat in mines, 108. 

Heavy spar, 448. 

Hematite, 19, 119, 120. 
occurrence of, 135, 302. 

Hindostan oilstone, 429. 

Hibernia, New Jersey, iron mine, 128. 

Horizontal shaft, 106. 

Hornblende, as a rock-forming min- 
eral, 7, 10. 

Horn silver, 21. 

Horse, 99. 

Hot springs, association of, with 
mineral veins, 86. 

Huancavelica, Peru, mercury mine, 
257. 



486 



INDEX. 



Huanchaca, Bolivia, silver mine, 195. 
Hungary, borax in, 435. 
gold in, 165. 

iron pyrite production of, 301. 
nickel production of, 296. 
salt production of, 434. 
Hydrated sesquioxide of iron, 119. 
Hydraulic cement, 387. 
analyses of, 388, 389. 
production of Indiana, 389. 
Kentucky, 389. 
New York, 387, 389. 
Pennsylvania, 390. 
United States, 389. 
Hydraulic elevator, 156. 
Hydraulic mining, 111, 155. 
Hydraulic mining, suspension of, 156. 



Idaho, gold production of, 173. 

lead in, 235. 

lead production of, 240, 241, 307. 

silver in, 190. 

silver production of, 204, 205, 307. 
Idria, Austria, mercury mine, 256. 
Igneous rocks, 34. 

Classification of, 35. 

position of, 37. 

the source of metals, 72. 

variation in, 34. 
Illinois, building-stone production of, 
383, 384, 386, 455. 

coal production of, 333, 334, 455. 

lead in, 229. 

limestone production of, 379, 380. 

mineral products of, 455. 

spelter production of, 250, 252. 
Imports of United States, asbestos, 
448. 

asphaltum, 357. 

cement, 390, 456. 

coal, 331, 456. 

copper, 225, 456. 

emery, 427. 

gems, 425. 

gold, 456. 

graphite, 441. 

gypsum, 405. 



Imports of United States, iron, 145, 
456. 

iron pyrite, 300. 

lead, 456. 

marble, 382. 

millstones, 428. 

mineral products, 456. 

mineral waters, 420. 

nickel, 296. 

precious stones, 456. 

silver, 456. 

sulphur, 440, 456. 

tin, 456. 
Impregnation ore deposits, 80, 88. 
India, gold in, 166. 

gold production of, 166, 174. 

mica in, 443. 

silver coinage of, 204. 
Indiana, building-stone production of, 
383, 384, 386. 

coal production of, 333. 

hydraulic cement production of, 
389. 

limestone production of, 379, 
380. 

natural gas in, 351. 

natural gas production of, 354, 
355. 

oilstones of, 429. 

petroleum in, 337. 

petroleum production of, 348. 
Indian Territory, coal production of, 

334. 
Indigenous soils, 391, 394. 
Infusoria, 426. 
Infusorial earth, 32, 425, 426. 

production of United States, 429. 
Intruded sheets, 37. 
Intrusive rocks, 37. 
Iowa, coal production of, 333, 455. 

gypsum production of, 405. 

limestone production of, 379. 

mineral production of, 455. 

zinc production of, 251. 
Iridium, 21,179. 
Iridosmium, 177, 179. 
Ireland, lead occurrence in, 237. 
Iron, 119. 

alloys of, 136 . 









INDEX. 



487 



Iron, association of manganese with, 
263. 
association with coal, 317. 
carbonate, 119. 
conditions necessary for profitable 

extraction of, 119. 
distribution of, 137. 
exports of, 145, 456. 
hat, 98. 

imports of, 145, 456. 
Mountain, Missouri, iron mines, 

126, 136, 143. 
native, 18, 81, 119. 
occurrence of, 18, 135, 302. 

Africa, 135. 

Asia, 135. 

Australia, 135. 

Austria, 134. 

Belgium, 134. 

Canada, 135. 

China, 135. 

foreign, 133. 

Germany, 134. 

Great Britain, 133. 

Italy, 135. 

Norway, 134. 

Portugal, 135. 

South America, 135. 

Spain, 134. 

Sweden, 134. 
ores of, 18, 119. 

manganiferous, 263. 
production of Alabama, 307. 

Colorado, 139, 143. 

Georgia, 139, 143. 

Germany and Luxemburg, 146. 

Great Britain, 146. 

Michigan, 138, 139, 144, 145, 
307, 455. 

Minnesota, 139, 142, 144, 145, 
455. 

Missouri, 139, 143. 

New Jersey, 139, 143. 

New York, 138, 141, 144, 145, 
307, 455. 

Ohio, 139, 143, 144. 

Pennsylvania, 138, 140, 144, 
145, 307, 455. 

Spain, 146. 



Iron production of Tennessee, 139, 
143. 

United States, 144, 145, 146, 
304, 305, 453. 

Virginia, 139, 142, 144, 145. 

West Virginia, 144. 

Wisconsin, 139, 142, 307, 455. 

World, 146. 
pyrite, 18, 119, 300. 

concretions of, 89. 

occurrence of, 301, 303. 

production of United States, 
300, 301, 304, 305. 

uses of, 300. 

as a source of sulphur, 438. 
treatises on, 460. 
uses of, 136. 
Italy, antimony production of, 298. 
asbestos in, 448. 
bauxite in, 285. 
copper in, 219. 
iron in, 135. 

iron pyrite production of, 301. 
lead in, 237. 
lead production of, 242. 
manganese in, 267, 268. 
manganese production of, 272. 
mercury in, 257, 261, 262. 
petroleum production of, 349. 
salt production of, 434. 
zinc in, 237, 246. 
zinc production of, 252. 



Japan, antimony production of, 298. 

copper in, 218, 220. 

copper production of, 226, 227. 

gold in, 166. 

petroleum in, 338, 340. 

petroleum production of, 349. 

silver coinage in, 204. 

silver production of, 206. 

sulphur in, 438. 
Jasper, use of, in jewelry, 423. 
Jean, Spain, lead district, 236. 
Jig, 112. 
Jigger, 112. 
Joint planes, 75. 



488 



INDEX. 



Joint planes in granite, 363, 364, 365. 
in sandstone, 371. 

Joplin district, Missouri, zinc depos- 
its, 244. 

Jura-Trias period of volcanic activity, 
68. 



K. 



Kansas, coal production of, 334. 

gypsum production of, 405. 

lead in, 229. 

lead production of, 241. 

limestone production of, 379. 

salt in, 431. 

salt production of, 433. 

spelter production of, 250. 

zinc in, 244. 

zinc production of, 250, 251, 307. 
Kaolin, 7, 10, 25, 399, 400. 
Karg gas well, Ohio, 352. 
Kentucky, asphaltum in, 356. 

coal in, 315. 

coal production of, 333. 

hydraulic cement production of, 
389. 

limestone production of, 379. 

natural gas in, 351. 

natural gas production of, 354. 

iron production of, 145. 
Kerosene oil, 340, 347. 
Keweenaw Point, Michigan, copper 

mines, 210, 220. 
Kootenay Lake, Canada, silver de- 
posits, 194. 
Krenmitz, Austria-Hungary, silver 
mines, 198. 



Ii. 



Laccolite, 37. 

Lake Champlain iron mines, 138, 142. 
Lake Superior region, copper mines 
of, 210, 212, 213, 221, 225. 
economic products of, 63. 
general features of, 63. 
iron ores of, 124, 138, 139, 140. 
Lakes desiccated in the Cordilleras, 
64. 



Lakes, Quaternary, 70. 

La Motte, Missouri, nickel mine, 292. 

Lampblack, 353. 

Lancaster Gap, Pennsylvania, nickel 

mines, 293, 296. 
Land plaster, 403. 
Land rock, 407. 
Lateral secretion, 86. 
Latin Union, formation of, 201. 
Laurel Creek, Georgia, corundum of, 

427. 
Lead (a leader), 99. 
Lead, 228. 

alloys of, 239. 

exports of, 456. 

imports of, 456. 

mineralogical association of, 228, 

238. 
occurrence of, 238, 302. 

Appalachian district, 229. 

Arizona, 255. 

Austria-Hungary, 237. 

Belgium, 237. 

Colorado, 233. 

Prance, 237, 238. 

Germany, 236. 

Great Britain, 237. 

Idaho, 235. 

Illinois, 229. 

Ireland, 237. 

Italy, 237. 

Kansas, 229. 

Mexico, 238, 240, 241. 

Missouri, 229. 

Mississippi valley 228, 229, 231, 

248. 
Montana, 235. 
New Mexico, 236. 
New South Wales, 238. 
Poland, 237. 
Portugal, 236. 
Russia, 237. 
Scotland, 237. 
Spain, 236. 
Sweden, 237. 
Utah, 235. 
Wales, 237. 
Wisconsin, 229. 
ores of, 22, 238. 









INDEX. 



489 



Lead production of, 239. 

Appalachian states, 2-40. 
Arizona, 240, 241. 
Austria-Hungary, 242. 
California, 240. 
Canada, 242. 

Colorado, 240, 241, 307, 455. 
Germany, 242. 
Great Britain, 242, 243. 
Idaho, 240, 241, 307. 
Italy, 242. 
Kansas, 241. 
Mexico, 242, 243. 
• Missouri, 241, 307, 455. 
Mississippi valley, 240. 
Montana, 240, 241, 307. 
New Mexico, 240, 241. 
Nevada, 240, 241. 
New South Wales, 242, 243. 
Russia, 242. 
Spain, 242, 243. 
Sweden, 242. 
United States, 240, 241, 242, 

243, 304, 305, 453. 
Utah, 240, 241, 307, 455. 
Wisconsin, 241. 
world, 242. 
price of, 239. 
treatises on, 461. 
uses of, 238. 
Lead-zinc, gash vein deposits, 84. 
Leader, 88. 

Leadville, Colorado, copper occur- 
rence, 216. 
manganese occurrence, 263, 

265. 
silver-lead mines, 189, 205, 233. 
Ledge, 98. 

Lehigh, Pennsylvania, anthracite area, 
316. 
County, Pennsylvania, brown he- 
matite, 121, 122. 
Lift plane in granite, 365, 366. 
Lignite, analyses of, 312. 

of Texas, 318. 
Lime, 359, 378, 379, 380. 
use as a fertilizer, 403. 
Limestone, 376. 

character of, 376, 377. 



Limestone, colour of, 377. 
definition of, 377, 378. 
distribution of, 385. 
flux, 453. 

occurrence of, 385. 
origin of, 31, 376. 
production of, Alabama, 379. 
California, 379. 
Connecticut, 380. 
Illinois, 379, 380. 
Indiana, 379, 380. 
Iowa, 379. 
Kansas, 379. 
Kentucky, 379. 
Maine, 379, 380. 
Maryland, 379. 
Massachusetts, 380. 
Minnesota, 379. 
Missouri, 379, 380. 
Nebraska, 379. 
New Jersey, 380. 
New York, 379, 380. 
Ohio, 379, 380. 
Pennsylvania, 379, 380. 
Texas, 379. 

United States, 379, 380, 453. 
Vermont, 379. 
Virginia, 379. 
Wisconsin, 379. 
use of term, 377. 
uses of, 378, 380. 
as a fertilizer, 402. 
Limonite, 19, 119, 120, 122, 135. 
Literature of Economic Geology, 457. 
Litharge, 238. 

production of United States, 449. 
Lithocarbon, 355. 
in Texas, 356. 
Lithographic stone, 442. 
Little Bay, Newfoundland, copper 

mines, 220. 
Locating mineral veins, 105. 
Lode, 98, 106. 
Longfellow, Arizona, copper mine, 

215. 
Long ton, 133. 
Los Cerrillos, New Mexico, turquoise 

in, 421. 
Louisiana, salt in, 431. 



490 



INDEX. 



Louisiana, salt production of, 433. 

sulphur in, 439. 
Lovelock's Station, Nevada, nickel 

mine, 292. 
Lower California, copper in, 220. 
Lubricating oil, 340, 347. 
Luxemburg and Germany, iron pro- 
duction of, 146. 

M. 

Magnesite, 14, 437. 
Magnetite, 19, 20. 

concentration of, 129. 
distribution of, 127. 
occurrence of, 128, 131, 302. 
Michigan, 127. 
New Jersey, 127. 
New York, 127. 
Pennsylvania, 127. 
Rhode Island, 128. 
origin of, 130. 
production of, 127. 
Michigan, 139, 144. 
New Jersey, 143, 144. 
New York, 141, 144. 
Pennsylvania, 141, 144. 
segregation of, 130. 
separation by electricity, 120. 
Maine, building-stone production of, 
383, 384, 386. 
copper production of, 225. 
granite production of, 368. 
limestone production of, 379, 380. 
slate production of, 376. 
Malachite, 22, 208. 
of Russia, 219. 
Malaspina glacier, Alaska, forest on, 

328, 329. 
Malay Peninsula, tin in, 279. 
Maltha, 355. 
Manganese, 253, 262. 
alloys of, 270. 
association with hot springs, 266. 

with iron, 263. 
concentration of, 269. 
distribution of, 262, 268. 
mineralogical association of, 262. 
occurrence of, 135, 263, 268, 303. 



Manganese, occurrence of, Appala- 
chian Mountains, 264. 

Arkansas, 263, 265. 

Australia, 267. 

California, 266. 

Canada, 266. 

Chili, 267. 

Cuba, 266. 

Europe, 267. 

France, 267. 

Georgia, 263, 264. 

Germany, 268. 

Great Britain, 267. 

Italy, 267, 268. 

Michigan, 265. 

New Jersey, 264. 

New Zealand, 267. 

Pennsylvania, 264. 

Portugal, 267. 

Russia, 267. 

Spain, 267. 

Sweden, 267. 

Turkey, 267. 

United States, 264. 

Vermont, 264. 

Virginia, 263, 264. 

Wisconsin, 265. 
ores of, 24. 
origin of, 268, 269. 
price of, 271. 
production of Arkansas, 271, 307. 

California, 271. 

Canada, 272. 

Chili, 272, 273. 

Colorado, 271. 

Cuba, 272. 

Georgia, 271, 307. 

Great Britain, 272. 

Italy, 272. 

Michigan, 272. 

New Jersey, 272. 

Portugal, 272. 

Russia, 272, 273. 

Sweden, 272. 

Turkey, 272. 

United States, 271, 272, 304, 
305. 

Vermont, 271. 

Virginia, 271, 307. 



INDEX. 



491 



Manganese, treatises on, 462. 

uses of, 270. 
Manganiferous iron ores, 263. 
silver ores, 263. 
zinc ores, 263. 
Mansfield, Germany, copper mines, 

218, 220, 222. 
Marble, character of, 39, 380. 
definition of, 377, 378. 
distribution of, 384. 
imports of, 382. 
occurrences of, 384. 
California, 381. 
Cordilleras, 381. 
Georgia, 381. 
Maryland, 381. 
New York, 381. 
Pennsylvania, 381. 
Tennessee, 381. 
Vermont, 380. 
Virginia, 381. 
production of California, 383. 
Georgia, 383. 
Maryland, 383. 
New York, 383. 
Pennsylvania, 383. 
Tennessee, 383. 
United States, 383, 386. 
Vermont, 383. 
uses of, 382. 
use of term, 377. 
Marbleized stone, 375. 
Marl, character of, 403. 

occurrence of, in New Jersey, 403. 
production of United States, 

403. 
use as a fertillizer, 402, 403. 
use in Portland cement, 403. 
Marquette iron district, 124, 140. 
Marsh gas, 350. 
Maryland, chromium in, 299. 
coal in, 315. 
coal production of, 333. 
granite production of, 368. 
infusorial earth in, 426. 
iron pyrite in, 301. 
limestone production of, 379. 
marble in, 381. 
marble production of, 383. 



Maryland, serpentine in, 382. 

slate production of, 376. 
Mason and Barry, Portugal, copper 

mine, 216. 
Massachusetts, building-stone pro- 
duction of, 383, 384, 386. 
granite production of, 368. 
limestone production of, 380. 
mineral water production of, 420. 
nickel in, 292. 

sandstone production of, 372. 
whetstones in, 428. 
Massive eruptive ore deposits, 80. 
McDonald petroleum field, Pennsyl- 
vania, 339. 
Mechanically formed ore deposits, 80, 

81, 135. 
Malaconite, 208. 
Menominee, iron district, 125, 140, 

143. 
Mercury, 24, 253. 

mineralogical association of, 253, 

258. 
occurrence of, 258, 303. 
Austria, 256. 
Borneo, 257. 
California, 253. 
Germany, 257. 
Italy, 257. 
Mexico, 258. 
Nevada, 253. 
New Mexico, 253. 
Oregon, 253. 
Peru, 257. 
Russia, 257. 
Servia, 257. 
Spain, 255. 
Utah, 253. 
origin of, 258. 
production of, 261. 
Austria, 261, 262. 
California, 255, 307, 455. 
Borneo, 261. 
Italy, 261, 262. 
Mexico, 261. 
Peru, 261. 
Bussia, 261. 
Servia, 261. 
Spain, 261, 262. 



492 



INDEX. 



Mercury production of United States, | 
261, 262, 304, 305, 453. 
world, 261, 262. 
price of, 260. 
treatises on, 461. 
uses of, 113, 260, 262. 
Merionetshire, England, manganese 

deposits, 267. 
Mesaba Kange iron district, 126, 140, 

142. 
Metalloids, 96. 
Metallurgy, 113. 

of aluminum, 286, 287. 
treatises on, 465. 
Metals, 96. 

in igneous rocks, 72. 
in sedementary rocks, 73. 
production of, California, 305. 
Colorado, 305. 
Cordilleras, 306. 
Montana, 305. 

United States, 304, 305, 306, 
307, 454. 
review of, 302, 304. 
Metamorphic rocks, 38. 
geological age of, 41. 
kinds of, 39. 
Metamorphism, causes of, 38, 40. 

contact, 92. 
Metric ton, 133. 
Mexico, copper in, 220. 

copper production of, 226. 
gold in, 167. 
gold production of, 175. 
lead in, 238, 240, 241. 
lead production of, 242, 243. 
mercury in, 258. 
mercury production of, 261. 
onyx in, 382. 
silver coinage of, 204. 
silver in, 193, 199. 
silver production of, 194, 206. 
tin in, 281. 

tin production of, 283. 
Mica, 8, 10, 442. 

occurrence of, in Canada, 443, 
444. 
India, 443. 
New Hampshire, 443. 



Mica, occurrence of, in North Caro- 
lina, 443. 
South Dakota, 443. 
Wyoming, 443. 
production of New Hampshire, 
444. 
North Carolina, 444. 
United States, 444, 445. 
Micaceous hematite, 119. 
Michigan, bromine in, 434. 
copper in, 209, 211. 
copper production of, 209, 213, 224, 

225, 307, 455. 
grindstones in, 427. 
gypsum production of, 405. 
iron in, 124, 127. 
iron production of, 138, 139, 144, 

145, 307, 455. 
manganese production of, 272. 
manganiferous iron ores in, 265. 
mineral production of, 455. 
mineral water production of, 420. 
salt in, 432. 

salt production of, 433, 455. 
sandstone production of, 372. 
silver production of, 192. 
Mill, 107. 
Millerite, 26, 292. 
Millstones, 425, 427. 
imports of, 428. 
occurrence of, New York, 428. 
Pennsylvania, 428. 
Virginia, 428. 
Mine, character of, 105. 

drainage of, 106. 
Mines, heat in, 106. 
Mining methods, 103, 
treatises on, 464. 
terms, 96. 
Mineral, definition of, 2, 96. 
paints, 449. 

occurrence of, in New York, 
450. 
Pennsylvania, 450. 
products, exports of, 456. 
imports of, 456. 
of California, 455. 
Colorado, 455. 
Illinois, 455. 



INDEX. 



493 



Mineral products of Iowa, 455. 
Michigan, 455. 
Minnesota, 455. 
Missouri, 455. 
Montana, 455. 
Nevada, 455. 
New York, 455. 
Ohio, 455. 
Pennsylvania, 455. 
United States, 450, 451, 453, 

454, 455, 456. 
Utah, 455. 
Wisconsin, 455. 
statistics, treatises on, 464. 
Mineral veins, 98. 
formation of, 85. 
in joint planes, 76. 
Mineral waters, classification of, 
418. 
imports of, 420. 
production of, California, 420. 
Colorado, 420. 
Massachusetts, 420. 
Michigan, 420. 
New Hampshire, 420. 
New York, 420. 
United States, 420, 453. 
Virginia, 420. 
Wisconsin, 420. 
treatises on, 464. 
Minerals, alteration of, 75. 
common rock-forming, 5. 
common vein-forming, 15. 
Mineralogy, text-books on, 459. 
Mineville, New York, iron mines of, 

129. 
Minnesota, building-stone production 
of, 383, 384, 386, 455. 
iron in, 124, 125, 126. 
iron production of, 139, 142, 144, 

145, 455. 
limestone production of, 379. 
mineral products of, 455. 
sandstone production of, 372. 
Mississippi valley, lead-zinc mines, 
84, 228, 229, 231, 240, 244, 
248. 
Missouri, barite in, 448. 
barite production of, 449. 



Missouri, building-stone production 
of, 383, 384, 386, 455. 

coal production of, 333, 455. 

iron production of, 139, 143. 

lead-zinc deposits of, 229, 244. 

lead production of, 241, 307, 455. 

limestone production of, 379, 380. 

mineral paints in, 450. 

mineral products of, 455. 

nickel in, 292. 

sandstone production of, 372. 

spelter production of, 250. 

zinc-lead deposits of, 229, 244. 

zinc production of, 250, 251, 307, 
455. 
Moisture in the Carboniferous, 328. 
Molly Gibson, Colorado, silver mines, 

189. 
Monocline, 51. 
Montana, asbestos in, 448. 

copper in, 209, 214. 

copper production of, 215, 224, 
225, 307, 455. 

diamonds in, 422. 

gold in, 158. 

gold production of, 173, 307, 455. 

lead in, 235. 

lead production of, 240, 241, 455. 

metal production of, 305. 

mineral production of, 455. 

sapphire in, 422. 

silver in, 181, 190. 

silver production of, 204, 205, 307, 
455. 
Mother Lode, California, 150, 152. 
Mountains, association of ores with, 

60, 94. 
Murcia, Spain, lead district, 236. 
Muscovite, 8, 443. 

Mysore, India, gold production of, 
166. 



N. 



Napa Consolidated, California, mer- 
cury mines, 255. 
Naphtha, 341, 347. 
Native copper, 22, 211. 
iron, 18, 81, 119. 



494 



INDEX. 



Native mercury, 24. 

silver, 21, 180. 
Natural gas, 337, 349. 
analyses of, 350. 
association of, with petroleum, 

351. 
consumption of, 354. 
distribution of, 337, 350, 351. 
future of, 352, 353. 
history of, 351. 
occurrence of, 337, 350. 
California, 351. 
China, 352. 
Indiana, 351. 
Kentucky, 351. 
New York, 351. 
Pennsylvania, 351. 
Ohio, 351, 352. 
Ontario, 352. 
pressure of, 352. 
production of Canada, 355. 
Indiana, 354, 355. 
Kentucky, 354. 
New York, 354. 
Ohio, 354, 355, 455. 
Pennsylvania, 354, 355, 455. 
United States, 354, 355, 453. 
West Virginia, 351, 354. 
uses of, 353, 354. 
Natural soda, 437. 
Nebraska, limestone production of, 

379. 
Nevada, antimony in, 297. 

antimony production of, 307. 

borax in, 435. 

borax production of, 436. 

gold in, 159. 

gold production of, 173, 307, 455. 

lead production of, 240, 241. 

mercury in, 253. 

mineral products of, 455. 

nickel in, 292. 

salt in, 430. 

silver in, 181. 

silver production of, 181, 204, 205, 

307, 455. 
sulphur in, 438. 
New Almaden, California, mercury 
mine, 253, 254, 255. 



New Birmingham, Texas, iron mine, 

121. 
New Brunswick, manganese in, 266. 
New Caledonia, cobalt in, 293, 294. 

cobalt production of, 296. 

nickel in, 292, 293, 294. 

nickel production of, 296. 
New England, anthracite production, 
321. 

bog iron ores of, 121. 

coal basin, 313, 314. 

granite production of, 368. 

infusorial earth in, 426. 

iron pyrite in, 301. 

slate in, 374. 

tin in, 275. 
Newfoundland, copper in, 220. 

iron pyrite in, 301. 
New Hampshire, copper in, 225. 

granite production of, 368. 

infusorial earth in, 426. 

mica in, 443. 

mica production of, 444. 

mineral water production of, 420. 

oilstones in, 428. 

soapstone in, 445. 

soapstone production of, 446. 

whetstones in, 428. 
New Idria, California, mercury mine, 

253, 254, 255. 
New Jersey, bluestone production of, 
373. 

building-stone production of, 383, 
384, 386. 

granite production of, 368. 

infusorial earth in, 426. 

iron in, 120, 127, 128, 135. 

iron production of, 139, 143, 144, 
145. 

limestone production of, 380. 

manganese production of, 272. 

manganiferous zinc ores of, 264. 

marl in, 403. 

soapstone in, 446. 

sandstone in, 369. 

sandstone production of, 372. 

spelter production of, 250. 

zinc in, 243, 244, 248. 

zinc production of, 250, 251. 



INDEX. 



495 



New Mexico, anthracite in, 311, 319. 

copper in, 216. 

copper production of, 224. 

gold production of, 173. 

lead in, 236. 

lead production of, 240, 241. 

mercury in, 253. 

silver in, 191. 

silver production of, 204. 

turquoise in, 421. 

zinc in, 251. 
New South Wales, gold in, 162. 

gold production of, 162. 

lead in, 238. 

lead production of, 242, 243. 

platinum in, 177. 

tin in, 280. 
New York, bluestone production of, 
373. 

building-stone production of, 383, 
384, 386, 455. 

cement production of, 455. 

granite production of, 368. 
^gypsum production of, 405. 

hydraulic cement production of, 
387, 389. 

t ron in, 127. 

iron production of, 138, 141, 144, 
145, 307, 455. 

limestone production of, 379, 380. 

marble in, 381. 

marble production of, 383. 

millstones in, 428. 

mineral paints in, 450. 

mineral products of, 455. 

mineral water production of, 420. 

natural gas in, 351. 

natural gas production of, 354. 

petroleum in, 338, 339. 

petroleum production of, 348, 349. 

Portland cement production of, 
390. 

salt in, 431, 432. 

salt production of, 433, 455. 

sandstone production of, 371. 

slate production of, 376. 
New Zealand, gold in, 162. 

gold production of, 162. 

manganese in, 267. 



New Zealand, petroleum in, 338, 340. 

platinum in, 177. 
Niccolite, 26, 292. 
Niccoliferous pyrrhotite, 26, 292. 
Nickel, 292. 
alloys of, 294. 
cobalt, association of, 293. 
copper alloy, 295. 
imports of, 296. 
mineralogical association of, 292, 

294. 
occurrence of, 292, 293, 294, 303. 
Austrian-Hungary, 293. 
Colorado, 292. 
Connecticut, 292. 
Great Britain, 293. 
Massachusetts, 292. 
Missouri, 292. 
Nevada, 292. 

New Caledonia, 292, 293, 294. 
North Carolina, 292. 
Norway, 293. 
Oregon, 292. 
Pennsylvania, 293, 294. 
Prussia, 293. 
Sweden, 293. 
ores of, 26. 
origin of, 294. 
price of, 295. 
production of, 295. 
Pennsylvania, 307. 
United States, 295, 304, 305. 
world, 296. 
steel alloy, 295. 
uses of, 294. 
Nijne-Taguilsk, Russia, copper mines, 

219. 
Non-metallic mineral production of 

United States, 454. 
Normal fault, 50. 
Norrie, Michigan, iron mine, 140. 
North America, copper production of, 

226, 227. 
North Carolina, barite production of, 
449. 
diamonds in, 423. 
gold in, 148. 
iron pyrite in, 301. 
mica in, 443. 



496 



INDEX. 



North Carolina, mica production of, 
444. 

nickel in, 292. 

phosphates in, 407, 408, 409. 

tin in, 275. 
Northern coal area, 313, 318. 

production of, 321. 
Norway, copper in, 219. 

iron in, 134. 

nickel-cobalt in, 293. 

nickel production of, 296. 

silver in, 199. 
Novaculites, occurrence in Arkansas, 

428. 
Nova Scotia, coal in, 314. 

gold in, 168. 

manganese in, 266. 
Nuggets, origin of, 157. 



O. 

Ochre, 450. 

production of United States, 450. 
Ogdensburg, New Jersey, zinc de- 
posits, 244. 
Ohio, building-stone production of, 
383, 386, 455. 
coal in, 315. 

coal production of, 333, 334, 455. 
grindstones in, 427. 
gypsum production of, 405. 
iron ore in, 132. 
iron production of, 139, 143, 144, 

145. 
limestone production of, 379, 380. 
mineral production of, 455. 
natural gas in, 351, 352. 
natural gas production of, 354, 355, 

455. 
petroleum in, 337, 338, 339. 
petroleum production of, 348, 349, 

455. 
salt production of, 433. 
sandstone production of, 371, 372. 
Oil-pools, 342. 
Oilstones, 428. 

occurrence of, Arkansas, 428. 
Indiana, 429. 
New Hampshire, 428. 



Oilstones, production of United States, 

429. 
Old Dominion, Arizona, copper mine, 

216. 
Olivine, 10. 
Ontario, natural gas in, 352. 

Utah, silver mine, 190. 
Onyx, 381, 382. 

occurrence of, Arizona, 382. 
California, 382. 
Mexico, 382. 
Oolitic iron ore, 123. 
Ooze, globigerina, 31. 

red, 31. 
Opal, occurrence of, Washington, 423. 
production of United States, 424. 
Openings, 230. 

Oregon, gold production of, 173. 
mercury in, 253. 
nickel in, 292. 
platinum in, 176. 
silver in, 205. 
Ore channels, 80, 86. 
Ore, definition of, 15, 96. 
Ore deposits, association of, with 
mountains, 60, 94. 
with younger rocks, 94. 
classification of, 78. 
distribution of, 94. 
geological association of, 94. 
origin of, 72. 
Ore pulp, 111. 
Ores, character of, 15. 
common, 15, 17. 
concentration of, 103, 110. 
mining of, 108. 
occurrence of, 302, 304. 
aluminum, 25, 284. 
antimony, 26, 297. 
cobalt, 26, 292. 
copper, 22, 208. 
gold, 20, 147. 
iron, 18, 119. 
lead, 22, 228. 
manganese, 24, 262. 
mercury, 24, 253. 
nickel, 26, 292. 
silver, 21, 180. 
tin, 25, 274. 



INDEX. 



497 



Ores, occurrence of zinc, 23, 243. 

reduction of, 103, 113. 

removal of, 74. 

transportation of, 109. 

variations of, 102. 
Organic rocks, 31. 

soils, 393. 
Ornamental stones, 359, 360. 
Orthoclase, 8. 
Osmium, 21, 179. 
Outcrop, 97. 
Overthrust fault, 50. 
Overturned fold, 51. 
Oxygen in the earth's crust, 1. 
Ozokerite, 357. 



Pacific coast, coal field, 321. 

production of, 313, 319. 
Palatinate, Germany, mercury mines, 

257. 
Palaeozoic, history of the United 

States, 68. 
Palermo, New Hampshire, mica mines, 

443. 
Palladium, 179. 

Panulcillo, Chili, copper mines, 217. 
Paraffin, 340. 

Park City, Utah, silver mines, 190. 
Patio process, 196. 
Paving-blocks, 366. 
Pay gravels, 154. 
Pay streaks, 154. 
Pearls, 422. 
Peat, 311. 

analyses of, 312. 
bogs, 322. 

bog theory for origin of coal, 322. 
Pennsylvania, anthracite in, 315, 316. 
production of, 316, 333. 
bituminous coal production of, 333. 
bluestone production of, 373. 
building-stone production of, 383, 

386, 455. 
coal in, 315, 316, 317. 
coal production of, 315, 316, 333, 

334, 455. 
cobalt in, 293. 



Pennsylvania, chromium in, 299. 

granite production of, 368. 

hydraulic cement production of, 
390. 

iron in, 121, 127. 

iron production of, 138, 140, 141, 
144, 145, 307, 455. 

limestone production of, 379, 380. 

manganese in, 264. 

marble in, 381. 

marble production of, 383. 

millstones in, 428. 

mineral paints in, 450. 

mineral production of, 455. 

natural gas in, 351. 

natural gas production of, 354, 355, 
455. 

nickel in, 293, 294. 

nickel production of, 307. 

petroleum in, 337, 338, 339. 

petroleum production of, 348, 349, 
455. 

Portland cement production of, 
390. 

sandstone in, 369. 

sandstone production of, 371. 

slate production of, 376. 

soapstone in, 445. 

soapstone production of, 446. 

spelter in, 250. 

zinc in, 244, 245. 

zinc production of, 250, 251. 
Penokee- Gogebic iron district, 125, 

135. 
Perak, tin in, 279. 
Percussion table, 112. 
Peru, copper in, 218. 

gold production of, 166, 167. 

mercury in, 257. 

mercury production of, 261. 

petroleum in, 340. 

petroleum production of, 349. 

phosphate production of, 411. 

silver in, 196. 

silver production of, 196, 206. 
Petit Anse, Louisiana, salt deposits, 

431. 
Petrified wood, use of, in jewelry, 423. 
Petroleum, 337. 



498 



INDEX. 



Petroleum, accumulation of, 346. 
association of salt with, 432. 
character of, 340. 
composition of, 341. 
distribution of, 337, 342. 
exports of, 456. 
history of, 338. 
occurrence of, 337. 

California, 337, 338, 340. 

Canada, 338, 340. 

Caspian region, 338, 340. 

Colorado, 337, 338, 339. 

Indiana, 337. 

Japan, 338, 340. 

New York, 338, 339. 

New Zealand, 338, 340. 

Ohio, 337, 338, 339. 

Pennsylvania, 337, 339. 

Peru, 340. 

Eussia, 338, 340. 

United States, 338. 

West Virginia, 338, 339. 
origin of, 340. 
production of, 347. 

California, 348. 

Canada, 349. 

Colorado, 348. 

Germany, 349. 

Indiana, 348. 

Italy, 349. 

Japan, 349. 

New York, 348, 349. 

Ohio, 348, 349, 455. 

Pennsylvania, 348, 349, 455. 

Peru, 349. 

Eussia, 349. 

United States, 346, 348, 349, 
453. 

West Virginia, 348, 349. 

world, 349. 
resemblance to animal oils, 340. 
resemblance, in behaviour, to arte- 
sian water, 343. 
theories to account for accumula- 
tion of, 343. 
treatises on, 463. 
uses of, 346. 
Phosphates, 12, 402, 405, 407. 
analyses of, 409. 



Phosphates, occurrence of, Alabama, 
407. 
Belgium, 410. 
Florida, 407, 408. 
Prance, 410. 
North Carolina, 407. 
South Carolina, 407. 
origin of, 410. 
price of, 410. 

production of, Belgium, 411. 
Canada, 411. 
Chili, 411. 
Florida, 409. 
French Guiana, 411. 
Great Britain, 411. 
Peru, 411. 

South Carolina, 408. 
United States, 411, 412, 453. 
Uruguay, 411. 
Venezuela, 411. 
Phosphor bronze, 223. 
Phosphorus, injurious to iron, 119. 
Phyllite, origin of, 39. 
Pig iron, production of United States, 

304, 305, 455. 
Pinches, 101. 
Pipe lead, 238. 
Piston jigger, 112. 
Piston stamp, 110. 
Pitch, 100, 231. 
Plagioclase, 6. 
Plaster of Paris, 403. 
Platinum, 21. 

characters of, 177. 
coinage of, 177. 
group of metals, 179. 
occurrence of, 176, 303. 
California, 176. 
Canada, 177. 
Colombia, 177. 
Borneo, 177. 
Brazil, 177. 

British Columbia, 177. 
New South Wales, 177. 
New Zealand, 177. 
Eussia, 176. 
United States, 176. 
price of, 178. 
production of, 178. 



INDEX. 



499 



Platinum production of Canada, 178. 
Colombia, 178. 
Kussia, 178. 

United States, 178, 304, 305. 
uses of, 177, 178. 
Pleistocene glaciation, 70. 
Plumbago, 441. 
Plutonic rocks, 37. 
Pocket theory for accumulation of 

petroleum, 346. 
Pointed box, 112. 
Poland, lead in, 237. 

spelter production of, 252. 
zinc in, 237, 246. 
zinc production of, 252. 
Pools of oil, 342. 
Pope's Creek, Maryland, infusorial 

earth deposits, 426. 
Portland cement, 387. 
analyses of, 388, 389. 
production of, New York, 390. 
Pennsylvania, 390. 
United States, 389. 
use of marl for, 403. 
Portland, Connecticut, brownstone, 

370. 
Portsmouth, Rhode Island, coal mines, 

314. 
Portugal, copper in, 220, 226. 
copper production of, 226, 227. 
iron in, 135. 
lead in, 236. 
manganese in, 267. 
manganese production of, 272. 
silver coinage of, 204. 
tin in, 279. 
Potosi, Bolivia, silver mines, 195, 258. 

tin mines, 281. 
Potter's clays, 400, 401. 

production of United States, 453. 
Precious stones, 421. 
imports of, 425, 456. 
production of, United States, 424. 
treatises on, 464. 
Precipitated ore deposits, 80, 82, 135. 
Prescott, Arizona, onyx deposits, 382. 
Prospect Hill, Nevada, silver mine, 

187. 
Prospecting, 104. 



Prospector, 104. 

Prosser iron mine, Oregon, 122. 

Prussia, cobalt production of, 296. 

nickel-cobalt in, 293. 
Przibram, Austria, silver mines, 102, 

198. 
Pseudomorphs, 88. 
Psilomelane, 24, 262. 
Pyrargyrite, 21, 180. 
Pyrite, 300. 

production of, United States, 304, 
305. 
Pyrolusite, 24, 262. 
Pyroxene group, 8. 
Pyrrhotite, niccoliferous, 26. 



Q 



Quartz, gold-bearing, 169. 

gold mines of California, 148. 

importance of, as a rock-forming 
mineral, 5, 10. 

production of United States, 424. 

use of, in jewelry, 423. 

use of in pottery, 401. 
Quartzite, characters of, 39. 
Quaternary additions to the United 
States, 70. 

coastal plains, 52. 

economic products of, 54. 

lakes of Cordilleras, 70. 
Quebec, Canada, petroleum in, 340. 
Queensland, gold in, 162. 

gold production of, 162. 

tin in, 280. 
Quicksilver, 253. 
Quincy, Michigan, copper mine, 213. 



Rammelsberg district, Germany, 198, 

236. 
Ratio of silver to gold, 202. 
Red hematite, 19, 119. 
occurrence of, 302. 
Michigan, 124, 125. 
Minnesota, 124, 126. 
Missouri, 126. 
New York, 123. 



500 



INDEX. 



Red hematite, occurrence of, Wiscon- 
sin, 124. 
origin of, 126, 127. 
production of, 122. 
Alabama, 139, 144. 
Georgia, 143. 
Michigan, 139, 144. 
Minnesota, 142, 144. 
Missouri, 143. 
Pennsylvania, 141. 
Tennessee, 143. 
Wisconsin, 142, 144. 
Redington, California, mercury mine, 

255. 
Red lead production of United States, 

449. 
Red ochreous hematite, 19. 
Red ooze, 31. 

Reduction of ores, 103, 113. 
Reef, 98. 

Replacement ore deposits, 80, 87, 135. 
Residual soils, 391, 392, 394. 
Reverse fault, 50. 

Rhenish provinces, Germany, lead 
mines of, 236, 245, 246. 
zinc mines of, 236, 245, 246. 
spelter, production of, 252. 
zinc, production of, 252. 
Rhodium, 179. 

Rhode Island, anthracites of, 311, 
314, 441. 
granite production of, 368. 
magnetite in, 128. 
Ribbon structure, 98. 
Richmond, Massachusetts, limonite 
deposits, 122. 
Virginia, coal, 315. 
Rider, 99. 

Rift in granite, 363, 365, 366. 
Rio Grande, Texas, coal areas, 318. 
Rio Tinto, Spain, copper mines, 217, 

220. 
River gravels, 154. 
Rock, definition of, 97. 
phosphates, 407. 
salt, 430. 
Rocks, disintegration of, 391, 392. 
disturbance of, 48. 
divisions of, 28. 



Rocks, geological age of, 41. 

igneous, 34. 

sedimentary, 28. 

metamorphic, 38. 
Rocky Mountain coal area, 313, 319. 

production of, 321. 

period of formation of, 69. 

silver in, 192. 
Roll, 101. 

Roofing-slate, 374, 375, 376. 
Rosario, Chili, copper mines, 217. 
Rosiclare, Illinois, fiuorite deposits, 

440. 
Roxbury, Connecticut, siderite de- 
posits, 133. 
Ruby Hill, Nevada, silver mines, 187. 
Ruby silver, 21. 
Run, 100. 
Russia, coal in, 335. 

copper in, 219. 

copper production of, 226. 

gold in, 163. 

gold production of, 164, 174, 175. 

lead in, 237. 

lead production of, 242. 

manganese in, 267. 

mercury in, 257. 

petroleum in, 339, 340. 

petroleum production of, 349. 

platinum in, 176. 

platinum production of, 178. 

salt production of, 434. 

silver in, 199. 
Ruthenium, 179. 
Rutland, Vermont, marble in, 380. 

S. 

Saline springs, 419. 

Salisbury, Massachusetts, iron mines, 

142. 
Salt, 13, 430. 

association with gypsum, 404. 

petroleum, 337, 343, 432. 
lakes, as a source of salt, 430. 
occurrence in California, 430. 
Kansas, 431. 
Louisiana, 431. 
Michigan, 432. 






INDEX. 



501 



Salt, occurrence in Nevada, 430. 

New York, 431, 432. 

Utah, 430. 
origin of, 430, 431, 432. 
production of, California, 433. 

Canada, 434. 

Colombia, 434. 

Germany, 434. 

Great Britain, 434. 

Hungary, 434. 

Italy, 434. 

Kansas, 433. 

Louisiana, 433. 

Michigan, 433, 455. 

New York, 433, 455. 

Ohio, 433. 

Eussia, 434. 

Spain, 434. 

United States, 433, 434, 455. 

Utah, 433. 

West Virginia, 433. 

world, 434. 
treatises on, 464. 
uses of, 433. 
water, 337, 

association with petroleum, 337, 
343, 432. 
Sandhurst, Victoria, gold district, 161. 
Sandstone, 29, 369. 
colour of, 370. 
characters of, 369. 
distribution of, 369, 385. 
occurrence of, 369, 385. 

Central states, 369. 

Connecticut, 369. 

New Jersey, 369. 

Pennsylvania, 369. 
production of, California, 372. 

Colorado, 371, 372. 

Connecticut, 372. 

Massachusetts, 372. 

Michigan, 372. 

Minnesota, 372. 

Missouri, 372. 

New Jersey, 372. 

New York, 372. 

Ohio, 371, 372. 

Pennsylvania, 372. 

United States, 371, 372, 386. 



I Sandstone production of Wisconsin, 
372. 

quarrying of, 370. 

texture of, 370. 

uses of, 371. 

weathering of, 369. 
Sand, use of, for abrasive purposes, 

425. 
San Jacinto, California, tin mines, 276. 
San Luis Obispo, California, onyx 

of, 382. 
Sap of granite, 363. 
Sapphire, occurrence of, Montana, 422. 
North Carolina, 423. 

production of United States, 424. 
Satin spar, use of, in jewelry, 423. 
Saucon valley, Pennsylvania, zinc 

mines, 245. 
Schemnitz, Austria, silver mines, 198. 
Schist, characters of, 39. 
Schistose structure, origin of, 40. 
Schonfeld, Austria, tin mines, 279. 
Schuylkill, Pennsylvania, anthracite 

area, 316. 
Scotland, lead in, 237. 
Scythestones, 428. 
Segregated ore deposits, 80, 90, 135. 
Segregation, nature of, 90. 

of gold, 152, 170. 

of iron, 130, 135. 
Serpentine, 381, 382. 

occurrence of, Maryland, 382. 

origin of, 176. 
Servia, mercury in, 257. 

mercury production of, 261. 
Sesquioxide of iron, 119. 
Seville, Spain, copper of, 216. 
Sweden, zinc in, 246. 
Shafts, 106, 107. 

in Comstock Lode, 108. 
Shales, 29. 
Sheet lead, 238. 
Sheet mica, 444. 
Sheets of intruded rocks, 37. 
Shenandoah valley, Virginia, iron 
deposits, 122, 142. 

tin deposits, 275. 
Shoding, 104. 
Shoemaker's sandstone, 429. 



502 



INDEX. 



Short ton, 133. 
Shot lead, 239. 
Siberia, gold in, 163. 
Sicily, asphaltum in, 356. 
sulphur exports of, 440. 
sulphur in, 438. 
sulphur production of, 438. 
Siderite, 20, 119, 132. 
Sierra Nevada Mountains, period of 
formation of, 68. 
silver in, 192. 
slate in, 374. 
Silesia, Germany, lead-zinc deposits, 
236, 246. 
spelter production of, 252. 
zinc production of, 252. 
Silicon in the earth's crust, 1. 
Silver, 180. 

alloys of, 201. 

character of, 201. 

coinage of, 201, 205. 

decline in price of, 202. 

distribution of, 192. 

exports of, 456. 

extraction of, by amalgamation, 

113. 
free-coinage of, 202. 
imports of, 456. 
lead ores, 302. 
mineralogical association of, 199, 

200. 
native, 21. 

occurrence of, 180, 199, 200, 302. 
Appalachians, 192. 
Arizona, 191. 
Australasia, 197, 199. 
Austria- Hungary, 198, 199. 
Bolivia, 195. 
California, 191. 
Canada, 194. 
Central America, 194. 
Chili, 197. 
Colombia, 197. 
Colorado, 181. 
Cordilleras, 181. 
Europe, 197, 199. 
France, 198. 
Germany, 197, 199. 
Great Britain, 199. 



Silver occurrence of Idaho, 190. 

Mexico, 193, 194, 199. 

Montana, 181, 190. 

New Mexico, 191. 

Nevada, 181, 184, 188. 

Norway, 199. 

Peru, 196. 

Rocky Mountains, 192. 

Russia, 199. 

Sierra Nevada Mountains, 192. 

South America, 195, 199. 

South Dakota, 192. 

Spain, 198. 

Sweden, 199. 

United States, 181, 189, 199. 

Utah, 181, 190. 
ores of, 21. 

manganiferous, 263. 
origin of, 199, 200. 
production of Arizona, 204. 

Australasia, 206. 

Austria-Hungary, 198, 206. 

Bolivia, 196, 206. 

California, 204, 455. 

Central America, 206. 

Chili, 197, 206. 

Colombia, 206. 

Colorado, 204, 205, 307, 455. 

France, 206. 

Germany, 198, 206. 

Idaho, 204, 205, 307. 

Japan, 206. 

Mexico, 194, 206. 

Michigan, 192. 

Montana, 204, 205, 307, 455. 

Nevada, 181, 204, 205, 307, 455. 

New Mexico, 204. 

Peru, 196, 206. 

Spain, 206. 

United States, 204, 205, 206, 
304, 305, 453. 

Utah, 204, 205, 307, 455. 

world, 203, 206, 207. 
ratio of, to gold, 202. 
treatises on, 461. 
uses of, 201. 
Slate, 373. 

character of, 374. 
colour of, 373. 



INDEX. 



503 



Slate, consumption of, 375. 
distribution of, 374, 384. 
geological age of, 374. 
occurrence of, Appalachian states, 
374. 
California, 374. 
New England, 374. 
origin of, 39, 373. 
production of, Maine, 376. 
Maryland, 376. 
New York, 376. 
Pennsylvania, 376. 
United States, 376, 386. 
Vermont, 376. 
Virginia, 376. 
uses of, 374, 375. 
Slaty cleavage, 373, 374. 
Slickenside, 100. 
Slime, 111. 
Sluice, 111. 
Smaltite, 13, 26. 
Smelting, 113, 114. 
Sruithsonite, 23, 243. 
Smoky quartz, production of, United 

States, 424. 
Soapstone, 14, 445, 
occurrence of, 445. 
production of, New Hampshire, 
446. 
New Jersey, 446. 
Pennsylvania, 446. 
United States, 446, 447. 
Vermont, 446. 
uses of, 446. 
Soils, 391. 

classification of, 391. 
impoverishment of, 398. 
origin of, 391. 
treatises on, 463. 
Solenhofen, Germany, lithographic 

stone, 442. 
Solution cavities, 77. 
South Africa, gold in, 164. 
gold production of, 165. 
South America, copper production of, 
226, 227. 
gold in, 166. 
guano in, 406. 
iron in, 135. 



South America, natural soda in, 437. 

silver in, 195, 199. 

tin in, 280. 
South Carolina, barite production of, 
449. 

gold in, 148. 

gold production of, 173. 

iron pyrite in, 301. 

phosphate in, 407, 408, 409. 

phosphate production of, 408. 
South Dakota, artesian wells in, 418. 

gold in, 158. 

grindstones in, 427. 

granite production of, 368. 

gypsum production of, 405. 

mica in, 443. 

silver production of, 205. 
South Wallingford, Vermont, man- 
ganese mines, 264. 
Southern Atlantic states, tin in, 275. 

spelter production of, 250. 

zinc production of, 250, 251. 
Spain, antimony production of, 298. 

coal production of, 335. 

copper in, 209, 216, 220. 

copper production of, 226, 227. 

iron in, 134. 

iron production of, 146. 

iron pyrite in, 301. 

iron pyrite production of, 301. 

lead in, 236. 

lead production of, 242, 243. 

manganese in, 267. 

mercury production of, 255, 261, 
262. 

salt production of, 434. 

silver coinage of, 204. 

silver in, 198. 

silver production of, 206. 

spelter production of, 252. 

tin in, 279. 

zinc in, 236, 247, 

zinc production of, 252. 
Spanish gold mine, California, 151. 
Spathic iron ore, 119. 
Specular hematite, 19, 119. 
Spelter, 249. 

price of, 249. 

production of, Austria, 252. 



504 



INDEX. 



Spelter, production of, Belgium, 252. 

Eastern states, 250. 

Great Britain, 252. 

Illinois, 250, 252. 

Kansas, 250. 

Missouri, 250. 

New Jersey, 250. 

Pennsylvania, 250. 

Poland, 252. 

Rhine District, 252. 

Silesia, 252. 

Southern states, 250. 

Spain, 252. 

United States, 250, 252. 

world, 252. 
Sphagnum, action of, 322. 
Sphalerite, 23, 243. 
Sphene, occurrence of, New York, 

423. 
Spiegeleisen, 270. 
Springs, cause of, 412. 
Stamps, 110. 
Stamping of ores, 110. 
State geological surveys, value of, 

458. 
Statistics of minerals, treatises on, 

464. 
Statuary bronze, 222. 
Steatite, 445. 
Stibnite, 26, 297. 
St. Ives, England, tin mines, 278. 
Stockwerk, 89. 
Stoping, 107. 
Stora Kopparberget, Sweden, copper 

mines, 219. 
Straits Settlements, tin in, 279. 

tin production of, 283. 
Stratified, definition of, 28. 
Stream-tin , 25, 274. 
Strike, 51, 100. 
Strike fault, 50. 

Sublimation ore deposits, 80, 93. 
Submergence of land in Carboniferous 

period, 326. 
Sudbury, Canada, nickel mines, 293. 

platinum occurrence, 177. 
Sulphide of silver, 180. 
Sulphur, 12, 438. 

imports of, 440, 456. 



Sulphur injurious in iron ores, 119. 
occurrence of, Japan, 438. 
Louisiana, 439. 
Nevada, 438. 
Sicily, 438. 

United States, 438, 439. 
Utah, 438. 
origin of, 438. - 
production of, Sicily, 438. 

United States, 439. 
uses of, 439. 
Sulphur Bank, California, mercury 

mines, 86, 254, 255, 259. 
Sulphuric acid, use of iron pyrite for, 

300. 
Sumatra, tin in, 280. 
Surveys, state and national geological, 

457. 
Sutro tunnel, 107, 183. 
Swamp soils, 394. 
Sweden, copper in, 219. 
iron in, 134. 
lead in, 237. 
lead production of, 242. 
manganese in, 267. 
manganese production of, 272. 
nickel-cobalt in, 293. 
nickel production of, 296. 
silver in, 199. 
Swells, 101. 
Switzerland, aluminum production of, 

291. 
Syenite, use of, as granite, 366. 
Syncline, 51. 



T. 



Table Mountain, California, 154. 
Tailings, 112. 
Talc, 14, 445. 

production of, United States, 447. 
Talus soils, 394. 
Tamarack, Michigan, copper mine, 

213. 
Tarapaca, guano deposits, 407. 
Tasmania, gold in, 163. 

tin in, 280. 
Telluride of gold, 159. 
Tennessee, coal in, 315. 



INDEX. 



505 



Tennessee, coal production of, 334. 
iron production of, 139, 143. 
marble in, 381. 
marble production of, 383. 
Tertiary coal, 314, 318, 319. 
coastal plains, 54. 
land areas, 69. 
mountain folding, 69. 
river gravels, 154. 
Texas, artesian wells in, 418. 
asphaltum in, 356. 
coal in, 318. 
iron in, 121. 

limestone production of, 379. 
lithographic stone in, 442. 
silver production of, 205. 
Tharsis, Spain, copper mine, 217. 
Thermal springs, 418, 419. 
Thibet, borax in, 435. 
Thistle, Utah, ozokerite deposits, 357. 
Thunder Bay, Canada, silver mines, 

194. 
Ticonderoga, New York, graphite, 441. 
Tilly Foster mine, New York, titanite 

from, 423. 
Tilt Cove, Newfoundland, copper 

mine, 220. 
Timbering mines, 108. 
Time-scale, geological, 45. 
Tin, 274. 

alloys of, 282. 
distribution of, 274. 
imports of, 282, 456. 
mineralogical association of, 274, 

281. 
occurrence of, 274, 281, 303. 
Alabama, 275. 
Australia, 280. 
Austria, 279. 
Banca, 279. 
Billeton, 279. 
Bolivia, 280. 
Burmah, 280. 
California, 276. 
England, 277. 
Finland, 279. 
France, 278. 
Germany, 278. 
Mexico, 281. 



Tin, occurrence of, New South Wales, 
280. 
North Carolina, 275. 
Perak, 279. 
Portugal, 279. 
Queensland, 280. 
South America, 280. 
Spain, 279. 

Straits Settlements, 279. 
Sumatra, 280. 
Tasmania, 280. 
United States, 275, 277. 
Victoria, 280. 
Virginia, 275. 
origin of, 281. 
ores of, 25, 274. 
placers, 274. 
plate, 282. 
price of, 282. 

production of Australia, 283. 
Austria, 283. 
Bolivia, 283. 
Germany, 283. 
Great Britain, 283. 
Mexico, 283. 
Straits Settlements, 283. 
United States, 283, 304, 305. 
world, 283. 
treatises on, 462. 
uses of, 282. 
Titanite in New York, 423. 
Titusville, Pennsylvania, petroleum 

in, 338. 
Tombstone, Arizona, silver mines, 191. 
Tourmaline, 423, 424. 
Transported soils, 391, 395. 
Transvaal, gold in, 164. 
Treadwell, Alaska, gold mine, 160. 
Trenton limestone, as a source of 

petroleum, 337, 338, 339. 
Triassic coastal area, 56. 
economic products of, 57. 
volcanic activity of, 57. 
Tribute system, 109. 
Trinidad, asphaltum in, 356, 357. 
True veins, 80, 83. 
Tunnel, 106, 107. 
Turgite, 19. 
Turkey, manganese in, 267. 



506 



INDEX. 



Turkey, manganese production of ,272. 
Turquoise, 421. 

occurrence of New Mexico, 421. 

production of United States, 424. 
Tuscany, borax in, 435. 
Tye, 112. 
Type metal, 239, 297. 

U. 

Unitite, 355. 
Unconformity, 45, 46. 
Underlie, 100. 

United States, abrasive materials, 
production of, 429. 
agatized wood production of, 424. 
aluminum production of, 290. 
antimony production of, 298, 304, 

305. 
artesian wells in, 418. 
asbestos imports of, 448. 
asphaltum imports of, 357. 

production of, 357. 
barite production of, 449. 
bluestone production of, 386. 
borax production of, 436. 
bromine production of, 434. 
buhrstone production of, 429. 
building-stone production of, 383, 

385, 386, 453. 
catlinite production of, 424. 
cement exports of, 456, 
imports of, 390. 
production of, 453, 456. 
chromium in, 299. 

production of, 300, 304, 305. 
coal consumption of, 331. 
exports of, 456. 
imports of, 456. 
occurrence in, 312. 
production of, 320, 333, 334, 
335, 336, 456. 
cobalt production of, 296, 304, 

305. 
copper consumption of, 224. 
exports of, 456. 
imports of, 225, 456. 
occurrence in, 209. 
production of, 224, 225, 226, 
227, 304, 305, 453. 



United States, corundum production 

of, 429. 
diamond production of, 424. 
emery imports of, 427. 

production of, 429. 
feldspar production of, 401, 402. 
flint production of, 402. 
garnet production of, 424. 
gems, imports of, 425. 
geological history of, 65. 
geological survey, publications of, 

457. 
gold coinage of, 172. 

exports of, 456. 

imports of, 456. 

production of, 173, 174, 175, 
304, 305, 453. 
gold quartz production of, 424. 
granite production of, 368, 386. 

uses of, 367. 
graphite imports of, 441. 

production of, 441. 
grindstones, production of, 429. 
gypsum imports of, 405. 

production of, 405. 
hydraulic cement production of, 

389. 
in Archean times, 65. 

Cambrian times, 67. 

Cretaceous times, 69. 

Palseozoic times,. 68. 

Tertiary times, 69. 
infusorial earth production of, 

429. 
iron, exports of, 145, 456. 

imports of, 145. 

production of, 144, 145, 146, 
304, 305, 453. 
iron pyrite, production of, 300, 

301, 304, 305. 
lead, exports of, 456. 

imports of, 456. 

production of, 240, 241, 242, 
243, 304, 305, 453. 
lime production of, 453. 
limestone production of, 379, 386, 

453. 
litharge production of, 449. 
manganese, occurrence of, 264. 






INDEX. 



507 



United States, manganese production 
of, 271, 272, 304, 305. 
marble production of, 383, 386. 
marl production of, 403. 
mercury production of, 261, 262, 

304, 305, 453. 
metal production of, 304, 305, 306, 

307, 454. 
mica production of, 444, 445. 
millstones, imports of, 428. 
mineral products of, 450, 451, 453, 
454, 455. 
distribution of, 455, 456. 
exports of, 456. 
imports of, 456. 
mineral water, imports of, 420. 

production of, 420, 453. 
natural gas, consumption of, 
354. 
production of, 354, 355, 453. 
nickel production of, 295, 296, 304, 

305. 
ochre production of, 450. 
oilstone production of, 429. 
opal production of, 424. 
petroleum, exports of, 456. 
occurrence of, 338. 
production of, 346, 348, 349, 
453. 
phosphate production of, 411, 412, 

453. 
pig iron, 453. 
platinum production of, 178, 304, 

305. 
Portland cement production of, 

389. 
potter's clay production of, 453. 
precious stones, imports of, 456. 

production of, 424. 
quartz production of, 424. 
red lead production of, 449. 
salt production of, 433, 434, 453. 
sandstone production of, 371, 372, 

386. 
sapphire production of, 424. 
silver, coinage of, 204. 
exports of, 456. 
imports of, 456. 
occurrence in, 181, 189, 199. 



United States, silver production of, 
204, 205, 206, 304, 305, 453. 
slate production of, 376, 386. 
soapstone production of, 446, 

447. 
spelter production of, 250, 252. 
sulphur, imports of, 440, 456. 
occurrence in, 438, 439. 
production of, 439. 
talc production of, 447. 
tin, imports of, 456. 

occurrence in, 275, 277. 
production of, 283, 304, 305. 
tourmaline production of, 424. 
turquoise production of, 424. 
whetstone production of, 429. 
white lead production of, 449. 
zinc, occurence in, 244, 247. 

production of, 250, 251, 252, 
304, 305, 453. 
zinc-white, production of, 251, 
449, 453. 
United Verde, copper mine, Arizona, 

216. 
Upthrow of fault, 50. 
Urals, chromium in, 300. 
copper in, 219. 
gold in, 163. 
platinum in, 176. 
Uruguay, guano in, 407. 

phosphate production of, 411. 
Utah, artesian wells in, 418. 
asphaltum in, 356. 
copper in, 216. 
copper production of, 224. 
gold production of, 173. 
gypsum production of, 405. 
lead in, 235. 
lead production of, 240, 241, 307 r 

455. 
mercury in, 253. 
mineral products of, 455. 
ozokerite in, 357, 358. 
salt in, 430. 

salt production of, 433. 
silver in, 181, 190. 
silver production of, 204, 205, 307, 

455. 
sulphur in, 438. 



508 



INDEX. 



Vanner, 112. 

Vaseline, 347. 

Vegetable origin of coal, 322. 

Vegetation in Carboniferous, 325, 327. 

Vein, 98, 106. 

Vein rock, 97. 

Vein wall, 99. 

Veins, branching of, 102. 

effects of faults upon, 101. 

effects of intersections on, 102. 

influence of country rock upon, 
102. 

variations in, 101, 102. 
Veinstones, 17, 97. 
Venezuela, copper in, 217. 

copper production of, 175. 

phosphate production of, 411. 
Vermilion, 24. 

Vermilion Lake iron district, Minne- 
sota, 126, 140, 142. 
Vermont, building-stone production 
of, 383, 384, 386. 

copper in, 209. 

copper production of, 225. 

granite production of, 368. 

limestone production of, 379. 

manganese in, 264. 

manganese production of, 271. 

marble in, 380. 

marble production of, 383. 

soapstone production of, 446. 

slate production of, 376. 

whetstones in, 428. 
Vertical crevice opening, 230. 
Vete Grande, Mexico, silver mines, 

193. 
Vete Madre, Mexico, silver mines, 

193. 
Victoria, auriferous gravels of, 162. 
Victoria, gold in, 161, 162. 

gold production of, 161, 162. 

tin in, 280. 
Virginia, barite in, 448. 

barite production of, 449. 

coal in, 315. 

granite production of, 368. 

gypsum production of, 405. 

iron in, 121. 



Virginia, iron production of, 139, 
142, 144, 145. 

iron pyrite in, 301. 

limestone production of, 379. 

lithographic stone in, 442. 

manganese in, 263, 264. 

manganese production of, 271, 
307. 

marble in, 381. 

millstones in, 428. 

mineral paints in, 450. 

mineral water production of, 420. 

slate production of, 376. 

tin in, 275. 

zinc in, 245. 
Volcanic neck, 37. 

W. 

Wad, 24, 262. 
Wales, lead in, 237. 
Washington, coal in, 320. 

coal production of, 334. 

opal in, 423. 

silver production of, 205. 
Washita oilstones, 428. 
Water line, 102. 
Water, solvent power of, 74. 

underground, 74. 
Welcome nugget, 157. 

Stranger nugget, 157. 
Western coal area, 313, 318. 

production of, 321. 
Westphalia, Germany, lead mines, 

236. 
West Rutland, Vermont, marble in, 

380. 
West Virginia, bromine in, 434. 

coal in, 315. 

coal production of, 317, 333. 

iron production of, 144. 

natural gas in, 351. 

natural gas production of, 354. 

petroleum in, 338, 339. 

petroleum production of, 348, 349. 

salt production of, 433. 
Whetstones; 425, 428, 429. 
White lead, 238, 239. 

production of United States, 449. 



INDEX. 



509 



White metal, 249. 
Willemite, 23, 243. 
Winze, 107. 

Wisconsin, building-stone production 
of, 383, 384, 386, 455. 

granite production of, 368. 

iron in, 124. 

iron production of, 139, 142, 143, 
144, 307, 455. 

lead in, 229. 

lead production of, 241 . 

limestone production of, 379. 

manganiferous iron ore of, 265. 

mineral products of, 455. 

mineral water production of, 420. 

sandstone production of, 372. 

zinc production of, 251, 307. 
Witwatersrand gold district, Africa, 

165. 
World, antimony production of, 298, 
299. 

coal production of, 335. 

copper production of, 226, 227. 

gold production of, 174, 175, 203. 

iron production of, 146. 

iron pyrite production of, 301. 

lead production of, 242. 

manganese production of, 272. 

mercury production of, 261, 262. 

nickel production of, 296. 

petroleum production of, 349. 

salt production of, 434. 

silver production of, 203, 206, 207. 

spelter production of, 252. 

tin production of, 283. 

zinc production of, 252. 
Wurtzilite, 355. 
Wyoming, asbestos in, 447. 

gypsum production of, 405. 

mica in, 443. 
Wyoming, Pennsylvania, anthracite 
area, 316. 



Z. 



Zinc, 228, 243. 
blende, 23. 

mineralogical association of, 243, 
247. 



Zinc, occurrence of, 243, 244, 247, 
302. 

Austria-Hungary, 237, 246. 

Belgium, 237, 245. 

Cordilleras, 243. 

Europe, 247. 

Germany, 236, 245,246. 

Great Britain, 237, 246. 

Italy, 237, 246. 

Kansas, 244. 

Mississippi valley, 229, 244. 

Missouri, 244. 

New Jersey, 243, 244. 

Pennsylvania, 244, 245. 

Poland, 237, 246. 

Spain, 236, 247. 

Sweden, 246. 

United States, 244, 247. 

Virginia, 245. 
manganiferous, 263. 
ores of, 23. 

origin of, 84, 231, 244, 247, 248. 
price of, 249. 
production of, 249. 

Arkansas, 251. 

Austria, 252. 

Belgium, 252. 

Eastern states, 251. 

Great Britain, 252. 

Iowa, 251. 

Italy, 252. 

Kansas, 250, 251, 307. 

Missouri, 250, 251, 307, 455. 

New Jersey, 250, 251. 

New Mexico, 251. 

Pennsylvania, 250, 251. 

Poland, 252. 

Khine District, 252. 

Silesia, 252. 

Southern states, 250, 251. 

Spain, 252. 

United States, 250, 251, 252, 
304, 305, 453. 

Wisconsin, 251, 307. 

world, 252. 
treatises on, 461. 
uses of, 248. 
Zincite, 23, 243. 
Zinc white, 248, 251, 449, 453. 



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